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Gel Batteries - Starter?


bigfatmatt

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I’ve bought a boat, batteries are rubber ducked so I’m looking to replace them.

 

After doing some research it sounds like gel batteries last the longest and can handle deep discharge best (excluding lithium which is out of my price range right now). I understand I’ll need to replace the charger/regulator that’s on the current (open lead acid) batteries to prevent overcharging.

 

I’m currently looking at getting four of these Ritar lead-carbon gel batteries, along with this Victron charger/monitor. This would give me 330AH of leisure capacity and a starter.

 

However I’m getting conflicting information online about whether or not these are suitable as starter batteries. I’m running a Yamaha 9.9hp 4 stroke petrol outboard with electric start.

 

Would I be better off buying an AGM or sealed lead acid battery to use as a starter? How would I keep that isolated from the gel batteries since they have different needs for charging, whilst still allowing the alternator to charge the leisure batteries and the solar to charge the starter?

 

I’m quite new to boat electronics so any advice is welcome.

Edited by bigfatmatt
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Slightly off topic, but hw do you plan to keep the batteries charged ?

 

The 9.9 outboard will not do it - the alternator is far too small.

Do you have a generator or solar panels ?

 

The gel batteries will withstand a 'deeper' discharge than standard FLA batteries, but no way can you do 'deep discharges' without damaging the batteries and reducing their life.

 

I'd suggest that the reason the batteries are dead is beacuse you (or someone) has been trying to keep them charged with an outboard. Don't waste you money on expensive batteries, you will kill them as easily as cheap batteries - you need to do an electrical audit and find some method of recharging the batteries without relying on the outboard.

 

Are you a liveaboard or just a "day" user, and plug back into the marina mains at night ?

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In addition to Alan's observations and to try and answer part of the question, gel batteries generally have a much lower cold crank ability which makes them largely unsuitable for starters. AGM are better in that respect, but a standard LA battery would also serve well and be cheaper.

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Right now there’s a 200W solar panel on there but I’m planning to put 3x 330W solar panels on there before moving aboard. I do have a generator as well. Definitely not planning to use the alternator as a main source of charging.

 

Will be cruising in the good months with a marina mooring for winter (I need a residential address because I’m a company director so have to keep marina mooring all year round but wont be using it much in the good months). I don’t expect to do ‘deep discharges’ (if you mean beyond 50% DOD) very often — my electricity usage is quite light (iPad, phone charger, 12V fridge, couple hours of 12V TV, lights and water pump) — I was more looking at the 1500 cycles rating for gel vs 300 cycles for open lead acid.

 

I think what’s happened with the old batteries is the previous owners drained them, moored the boat in a shady spot and barely checked on it for a couple of years. They’re completely dead, wont hold a charge. I got about 5 mins of lights after giving them a full charge off mains.

 

 

13 minutes ago, PCSB said:

In addition to Alan's observations and to try and answer part of the question, gel batteries generally have a much lower cold crank ability which makes them largely unsuitable for starters. AGM are better in that respect, but a standard LA battery would also serve well and be cheaper.

 

Cheers, how would it be best to manage having an AGM + 3 gel batteries? I’m looking specifically at how to make sure leisure stuff can’t draw from the starter but making sure the solar or generator will still charge all 4.

Edited by bigfatmatt
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Sounds like by the time you move aboard you'll be sorted.

 

I would however still suggest that for your 1st purchase you get FLA batteries as you may still kill them until you learn how to manage your electicity.

 

Far better to waste £300 than (say) 3 or 4 times that with 'high spec' 'deep cycle' gel batteries.

 

You can find a stadard FLA for around £100, but decent quality Deep Discharge Gels could be £300

Yes you can find 100Ah gels for £150 but what are you getting ?

 

A quality 97Ah Gel (500x deep cycle) battery as used in a mobility scooter ...........................

 

MK-Battery GEL 100AH 12V (Dual Terminal) Mobility Smart

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15 minutes ago, bigfatmatt said:

 

 

Cheers, how would it be best to manage having an AGM + 3 gel batteries? I’m looking specifically at how to make sure leisure stuff can’t draw from the starter but making sure the solar or generator will still charge all 4.

The easiest way is to use all the same tech batteries, e.g. AGM, otherwise you are into charger splitting by a variety of devices. For example split charge diodes, or split charge relays etc. There are better qualified people on here then me so hopefully they will chime in.

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It does of course depend on daily power usage but if the usage is low then I'd be buying one 100Ah LiFePO4 battery for the solar and a separate small lead acid to deal with the outboard. A basic car starter battery say 35ah will be more than enough for an outboard. 

 

Keep the charging systems separate. 

 

Buy a second lithium battery later. 

 

 

 

 

 

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13 minutes ago, Alan de Enfield said:

Sounds like by the time you move aboard you'll be sorted.

 

I would however still suggest that for your 1st purchase you get FLA batteries as you may still kill them until you learn how to manage your electicity.

 

Far better to waste £300 than (say) 3 or 4 times that with 'high spec' 'deep cycle' gel batteries.

 

You can find a stadard FLA for around £100, but decent quality Deep Discharge Gels could be £300

Yes you can find 100Ah gels for £150 but what are you getting ?

 

A quality 97Ah Gel (500x deep cycle) battery as used in a mobility scooter ...........................

 

MK-Battery GEL 100AH 12V (Dual Terminal) Mobility Smart

 

My main concern with FLAs is my batteries are in an awkward spot for topping up. The only place they really fit is under the stairs, and there’s nowhere to get above them so it’d be a case of disconnecting everything monthly to add distilled water.

 

Are sealed lead acids or AGMs (also a lot cheaper than gels) worth a look?

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As Alan de Enfield mentioned above the topic is how much power you use in a day from the batteries and how you intend to replace that power. 

 

This is the key. 

 

The battery bank can be as big as a mountain but it still needs charging. 

 

if the charging system is not up to the job a large bank will end up being at a low state of charge and with lead batteries this means scrap quite quickly. 

 

I'm a big fan of small battery banks. 

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1 minute ago, Alan de Enfield said:

 

The outboard should be charging its own battery so the domestics can be totally separated and have a charger dedicated to their charging profile.

Exactly. If he is putting on a lot of solar then the thing to do is get a MPPT set to LFP batteries and get one of the 100ah batteries such as the Fogstar product. There are others about. I don't know how good Fogstar are but Lithium batteries with proper BMS will be better than lead batteries for daily cycling. 

 

 

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4 minutes ago, bigfatmatt said:

Are sealed lead acids or AGMs (also a lot cheaper than gels) worth a look?

 

 

It is actually becoming increasingly difficult to find non-sealed lead acid batteries, and yes they are still cheap compared tomother technologies.

 

I reckon to pay £80-£100 for a lead acid 110Ah battery. and on my cruiser I have 6x 230Ah open FLA batteries and the ones I bought last year were £160 each

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It doesn't matter if you have 'too much solar' . This doesn't mean a larger battery is needed. The sun will come up the next day and charge the battery. 

 

If it doesn't then we have a lot more to worry about than batteries !

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41 minutes ago, bigfatmatt said:

my electricity usage is quite light (iPad, phone charger, 12V fridge, couple hours of 12V TV, lights and water pump)

 

Point of Order...

 

A 12v fridge is not "quite light" usage. They guzzle the power.

 

I used to find my 600W of solar would keep my 12v fridge going from about March to October.

 

Over winter, God turned the solar off. 

 

 

 

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3 minutes ago, MtB said:

 

Point of Order...

 

A 12v fridge is not "quite light" usage. They guzzle the power.

 

I used to find my 600W of solar would keep my 12v fridge going from about March to October.

 

Over winter, God turned the solar off. 

 

 

 

600w of solar to run a fridge? Something wrong there. 

 

 

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18 minutes ago, magnetman said:

It does of course depend on daily power usage but if the usage is low then I'd be buying one 100Ah LiFePO4 battery for the solar and a separate small lead acid to deal with the outboard. A basic car starter battery say 35ah will be more than enough for an outboard. 

 

Keep the charging systems separate. 

 

Buy a second lithium battery later. 

I’m not sure what’s considered low.

 

My daily driver for work is an iPad which pulls 8W if it’s charged and 21W while charging. That needs to run at least 8-9 hrs a day. I’ve been using my phone as a Wi-Fi hotspot (boat is GRP so signal is OK inside) but I’ll probably swap that out for a dedicated 5G router.

 

I do have a more powerful laptop (can draw up to 110W when charging) that I use for a couple of hours here and there but I have a Honda generator so if batteries & solar alone can’t manage that I can use it off the generator.

 

Beyond that there’s a small 12V fridge, 12V TV which I’ll probably have on for a couple of hours in the evening, all the lights are LED, and there’s a water pump.

 

I would love to go with lithium if that’s a good option.

Edited by bigfatmatt
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@MtB

 

Maybe this was an old electrolux 3 way fridge. Modern compressor types are massively more efficient. Something like 4 amps for 1/3 of the time so 4 x 8 is 32ah per day. 

 

600w of solar will provide far more than that in the lighter months. 

Edited by magnetman
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1 minute ago, magnetman said:

600w of solar to run a fridge? Something wrong there. 

 

 

 

Not really. 

 

When I had 300w, it would power the fridge from April to Sept. As I added more panels, the winter period when the solar would not cope got ever shorter.

 

 

 

As an off grid liver-board I didn't need to run my engine or genny EVER, for nine months of the year. 

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4 minutes ago, bigfatmatt said:

I’m not sure what’s considered low.

 

My daily driver for work is an iPad which pulls 8W if it’s charged and 21W while charging. That needs to run at least 8-9 hrs a day. I’ve been using my phone as a Wi-Fi hotspot (boat is GRP so signal is OK inside) but I’ll probably swap that out for a dedicated 5G router.

 

I do have a more powerful laptop (can draw up to 110W when charging) that I use for a couple of hours here and there but I have a Honda generator so if batteries & solar alone can’t manage that I can use it off the generator.

 

Beyond that there’s a small 12V fridge, 12V TV which I’ll probably have on for a couple of hours in the evening, all the lights are LED, and there’s a water pump.

 

I would love to go with lithium if that’s a good option.

As Alan said earlier you need to do a power audit. Daily use estimates.

 

200Wh for the ipad

100Wh for the phone?

 

360Wh for the fridge 

 

Telly lights and pumps 200Wh? 

 

Add together 

 

860Wh. Divide by 12 to get Amp hours. 

 

So it is around 75Ah per day. 

 

Quite a lot of power use there. 

 

I think there is an interesting argument for putting a small inverter on the engine battery and running the outboard at tickover. Interesting to see what it generates. If it was 5 amps of charge this could contribute to charging the laptop. Outboards don't make much power but they are very quiet and use very little fuel at tickover. 

 

Never tried it and maybe it is inefficient but it does seem potentially interesting. 

 

You will want mains electric in winter. 

 

 

 

 

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7 minutes ago, magnetman said:

As Alan said earlier you need to do a power audit. Daily use estimates.

 

200Wh for the ipad

100Wh for the phone?

 

360Wh for the fridge 

 

Telly lights and pumps 200Wh? 

 

Add together 

 

860Wh. Divide by 12 to get Amp hours. 

 

So it is around 75Ah per day. 

 

Quite a lot of power use there. 

 

I think there is an interesting argument for putting a small inverter on the engine battery and running the outboard at tickover. Interesting to see what it generates. If it was 5 amps of charge this could contribute to charging the laptop. Outboards don't make much power but they are very quiet and use very little fuel at tickover. 

 

Never tried it and maybe it is inefficient but it does seem potentially interesting. 

 

You will want mains electric in winter. 

 

 

 

 

 

Cheers, I will have mains from probably October to March (marina).

 

I’ll do a proper power audit next time I’m on the boat (it’s moored about 4hrs from my current location). I’m definitely not against running the generator in the darker months if it’s needed to keep the batteries topped up, much like how someone with an onboard and a proper alternator would run that for power.

 

I also have 4x 50,000mAh power banks that I can charge at pubs and coffee shops (I use those for camping at the moment).

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52 minutes ago, bigfatmatt said:

much like how someone with an onboard and a proper alternator would run that for power.

 

 

The difference being that running an inboard engine with a 100 amp alternator to replace your (say) 100Ah daily discharge, is going to take many hours less than running your outboard engine with a 7 or 9 amp alternator. Work it out.

 

The other aspect is that you will fairly quickly burn out your Outboard alternator as it will be running at max output continuously - the battery bank will be always demanding 100% of its output.

 

Just a question - do you know that it is the Lead Acid batteries that dictate how much charge they take from the alternator (up to its maximum output) rather than the alternator dictating to the batteries how much they can take ?

A 400Ah battery bank will still be drawing around 6 amps at 14.6 volts when it is considered to be fully charged. (1.5% of capacity)

Edited by Alan de Enfield
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32 minutes ago, Alan de Enfield said:

 

 

The difference being that running an inboard engine with a 100 amp alternator to replace your (say) 100Ah daily discharge, is going to take many hours less than running your outboard engine with a 7 or 9 amp alternator. Work it out.

 

I’m talking about running my petrol generator (Honda 22i 2kW portable generator), not my outboard, for top-up charging when solar wont give me enough. Sorry for the confusion, lots of power sources.

 

My understanding could be wrong but 100Ah daily discharge = 1200Wh so it shouldn’t take long to top that up off a 2000W generator on an October afternoon outside the marina. Obviously there will be some inefficiency because there’ll be voltage step down from 240V generator to 12V battery, and some more because the batteries just wont draw that much current off the generator.

 

I’m aware that the 9A alternator on the outboard isn’t going to make any meaningful contribution to the battery charge and isn’t going to be in any way fuel efficient, though I’d rather still take advantage of it when I’m running the engine for propulsion because ‘free’ power is always good. If I’m cruising for 4 hours, that’s 18-36Ah give or take that otherwise would be going nowhere.

 

32 minutes ago, Alan de Enfield said:

 

Just a question - do you know that it is the Lead Acid batteries that dictate how much charge they take from the alternator (up to its maximum output) rather than the alternator dictating to the batteries how much they can take ?

A 400Ah battery bank will still be drawing around 6 amps at 14.6 volts when it is considered to be fully charged. (1.5% of capacity)

 

I didn’t know that, I’d have assumed a full bank would draw nothing.

Edited by bigfatmatt
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With the charger you linked to it will take a while to recharge your daily use.

Somewhere about 15 -20hrs allowing for the fact that the charger won't be putting out 10amps for most of the time.

You would be better off running a much bigger charger to minimise your charging times, whatever the biggest charger  is you can run off that genset guessing at over 100amps.

Edited by Loddon
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1 hour ago, bigfatmatt said:

My understanding could be wrong but 100Ah daily discharge = 1200Wh so it shouldn’t take long to top that up off a 2000W generator on an October afternoon outside the marina. Obviously there will be some inefficiency because there’ll be voltage step down from 240V generator to 12V battery, and some more because the batteries just wont draw that much current off the generator.

 

This is NOT the way recharging batteries works

I have used 100Ah, therefore if I run my 100 Amp alternator (or battery charger via a generator) I can replace it in 1 hour.

 

O' NO. It doesn't work like that.

 

As a battery becomes to a higher level of charge it requires a higher voltage and so the current drops (W = A x V)

 

Just as an example (numbers for guidance only and to simplfy the maths)

 

Running the 100 amp alternator (or 100 amp battery charger)

 

The first 15 minutes you will be getting your '100 amps', so you will put approximately 25Ah into the batteries.

The voltage increase so the current drops and for the next 30 minutes you may get a charge of 50 amps, so another 25Ah in the battery

Then the voltage increase so the current drops and for the next hour you may get a charge of  20 amps, so another 20Ah in the battery.

Then the voltage increases and the current drops so for the next hour  you may get a charge of 10 amps so another 10Ah in the battery.

Now we are getting up to around 14.4 volts and the current drops to 6 amps so for the next 2 hours you get another 12 Ah in the battery.

 

Now you will find that the charging will sit at around 14.6 volts and 3 or 4 amps, Once your batteries have reached this steady state with neither the voltage or the current changing for at least 2 hours, the battery bank can be considerd to be 99.99% SoC.

 

So your 100 amp alternator has actually taken about 6hrs 45 minutes to replace the 100Ah used, and fully charge the battery.

Edited by Alan de Enfield
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