Gel Batteries - Starter?

[magnetman]

Lithium batteries do change this story somewhat.

[Alan de Enfield]

11 minutes ago, magnetman said:

Lithium batteries do change this story somewhat.

 

Indeed they do, but the discussion is about Lead Acid batteries.

He has said he may change over to Lithiums in the future.

[Tony Brooks]

41 minutes ago, bigfatmatt said:

 

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.

 

 

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

 

Really it is tell us the old, old story, as we have heard many times before. Your understanding is wrong.

 

Note what Alan told you. It is the BATTERIES that control the amount of charge they will accept, the charger just supplies what the batteries ask for.

 

Lithium batteries will accept all the current the charge source can throw at them, right up to the point of overcharge and the resultant destruction. Lead acids start to reduce the charge they will accept within, perhaps, 15 to 30 minutes of starting to charge and the reduction goes on and on until they will only accept perhaps an amp per 100Ah battery. This means that although a 2000 Watt generator may be capable of delivering 140 amps, it won't do that for long into Lead acid batteries. But in any case that generator will have to use a charger to charge the batteries and a 100 amp one will be expensive.

 

As a very rough guide, take half the alternator or charger's rated output as the average over two hours or so. From then on, the average will become less and less. Depending on bank size and depth of discharge, it will take anything for a few to many hours to fully recharge a lead acid battery bank.

 

A fully charged lead acid battery is likely to continue to draw between 1% and 2% of battery capacity, so Alan is about right depending upon bank capacity.

 

Once again - buy simple lead acid batteries while you learn how not to destroy them. What you say above suggest that you are well on course for battery destruction unless you heed what has been said. I am sure that the difference in price between your gels and ordinary LA batteries would pay for a battery monitor that will help you not destroy them - once you learn which scales are likely to be lies, so helping you with the battery destruction.

[magnetman]

1 minute ago, Alan de Enfield said:

 

Indeed they do, but the discussion is about Lead Acid batteries.

He has said he may change over to Lithiums in the future.

 

I think he might be able to consider a smaller bank and use a lithium battery.

 

3 x 110 AGM is not all that different from 1 x 100Ah LFP battery in price terms.

 

It all comes down to daily usage.

 

Whatever you do if you are not on mains power you have to charge the batteries. It seeems interesting to use a type of battery which can take a faster charge rate.

 

 

[Tony Brooks]

Just now, magnetman said:

 

I think he might be able to consider a smaller bank and use a lithium battery.

 

3 x 110 AGM is not all that different from 1 x 100Ah LFP battery in price terms.

 

It all comes down to daily usage.

 

Whatever you do if you are not on mains power you have to charge the batteries. It seeems interesting to use a type of battery which can take a faster charge rate.

 

 

 

Agreed, as long as you can reliably terminate charging before damage is done AND control the charge to protect the charging  device from overheating because of sustained high outputs. Both add complications not needed on LA batteries.

[cuthound]

My boat was specified with these Lifeline AGM's when new in 2007.

 

https://www.tayna.co.uk/marine-batteries/lifeline/gpl-4c/

 

It is still on its original batteries, but they have lost about 50% of their capacity in the past 16 years of leisure boating. However I know how to look after batteries having worked with them throughout my career.

 

They are excellent lead acid batteries but at todays prices Lithium batteries make more sense.

[bigfatmatt]

5 minutes ago, Tony Brooks said:

 

Agreed, as long as you can reliably terminate charging before damage is done AND control the charge to protect the charging  device from overheating because of sustained high outputs. Both add complications not needed on LA batteries.

 

Thanks, I understand how you’d stop charging from a generator (turn it off) but how would you terminate charging from solar? Do you physically disconnect the charger or can you buy chargers that will stop the charging if the batteries are full?

Edited May 15, 2023 by bigfatmatt

[Tony Brooks]

Just now, bigfatmatt said:

 

Thanks, how would you terminate charging from solar? Do you physically disconnect the charger or can you buy chargers that will stop the charging if the batteries are full?

 

Some solar controllers allow you to set custom voltage settings, so one way would be to set the float voltage to less than the fully charged battery voltage. From what I can see, lithiums increase the complexity of the control systems needed.

[bigfatmatt]

14 minutes ago, magnetman said:

 

I think he might be able to consider a smaller bank and use a lithium battery.

 

3 x 110 AGM is not all that different from 1 x 100Ah LFP battery in price terms.

 

It all comes down to daily usage.

 

Whatever you do if you are not on mains power you have to charge the batteries. It seeems interesting to use a type of battery which can take a faster charge rate.

 

I could buy LiFePo4, I’m honestly just terrified of wrecking them whereas if I wreck £500-600 worth of batteries it’s a write-off I can deal with as a cost of the learning process.

 

I have about £3k to buy new solar panels, batteries, an MPPT controller and any accessories to help me not to destroy the whole bank.

Edited May 15, 2023 by bigfatmatt

[rusty69]

1 minute ago, Tony Brooks said:

 

Some solar controllers allow you to set custom voltage settings, so one way would be to set the float voltage to less than the fully charged battery voltage. From what I can see, lithiums increase the complexity of the control systems needed.

To add to this, some controllers can have their absorption voltage and duration altered, as well as the float voltage, though some people advocate that the BMS should act as a charge control device.

[MtB]

27 minutes ago, bigfatmatt said:

 

I have about £3k to buy new solar panels, batteries, an MPPT controller and any accessories to help me not to destroy the whole bank.

 

The best and most powerful accessory for achieving this is free, and you already have one.

 

It's your brain, along with some time. Probably quite a lot of time but there are no short-cuts. Use your brain and your time to read the "Battery Charging Primer" here that no-one has pointed so far yet in this thread (link below).

 

Once you've read it several times over, understood and properly digested it, you'll have all the knowledge necessary to manage your batteries without destroying them.

 

 

 

 

 

[magnetman]

Victron Smartsolar MPPT controllers allow you to set the voltage. Once the batteries are charged nothing else will come from the solar panels.

 

I've got 1kw of solar on one boat and 1.3kw on the other one. Both of these arrays go via Victron MPPT Smartsolar (bluetooth app) and the batteries are almost always full. Doesn't matter if they are full it just effectively switches the solar panels off.

 

Not an issue. Odd having loads of surplus but some people direct this to hot water. I don't wash so not needed.

 

Basically a LiFePO4 battery with a BMS and a Victron MPPT plus solar panels is the way to go.

 

 

 

 

[rusty69]

5 minutes ago, magnetman said:

Not an issue. Odd having loads of surplus but some people direct this to hot water. I don't wash so not needed.

Rumour has it you were forced to wash last year when you fell in the river.

[magnetman]

Just now, rusty69 said:

Rumour has it you were forced to wash last year when you fell in the river.

Yes. This was August the 12th if I remember right. Fell in a shallow backwater and became concerned about the Weils disease so I did interact with clean water for a short spell. 

 

Very worrying. 

 

They don't let one use car washes unless one has a car. 

[cuthound]

28 minutes ago, magnetman said:

They don't let one use car washes unless one has a car. 

 

You should try using the one this dog uses...

 

 

 

 

[bigfatmatt]

3 hours ago, magnetman said:

Victron Smartsolar MPPT controllers allow you to set the voltage. Once the batteries are charged nothing else will come from the solar panels.

 

I've got 1kw of solar on one boat and 1.3kw on the other one. Both of these arrays go via Victron MPPT Smartsolar (bluetooth app) and the batteries are almost always full. Doesn't matter if they are full it just effectively switches the solar panels off.

 

Not an issue. Odd having loads of surplus but some people direct this to hot water. I don't wash so not needed.

 

Basically a LiFePO4 battery with a BMS and a Victron MPPT plus solar panels is the way to go.

 

Any recommendation on which LiFePO4 batteries and BMS to look at?

 

Should I also have an AGM to start the outboard and just keep that completely separate?

[nicknorman]

56 minutes ago, bigfatmatt said:

 

Any recommendation on which LiFePO4 batteries and BMS to look at?

 

Should I also have an AGM to start the outboard and just keep that completely separate?

An outboard starter battery will barely become discharged at all, unless there is a problem starting it. I suggest an ordinary flooded lead acid battery (either open or sealed) is the best thing to use for a starter battery. No point in buying an expensive AGM or gel battery if you aren’t going to use the advantages of them.

 

We are all-lithium for the domestic batteries but still have a sealed wet lead acid battery for starting the Beta 43.

Edited May 15, 2023 by nicknorman

[bigfatmatt]

40 minutes ago, nicknorman said:

An outboard starter battery will barely become discharged at all, unless there is a problem starting it. I suggest an ordinary flooded lead acid battery (either open or sealed) is the best thing to use for a starter battery. No point in buying an expensive AGM or gel battery if you aren’t going to use the advantages of them.

 

We are all-lithium for the domestic batteries but still have a sealed wet lead acid battery for starting the Beta 43.

Thanks, how should I size the starter for a 9.9kW 4 stroke petrol outboard? I assume it doesn’t need a 110Ah battery?

[Alan de Enfield]

1 minute ago, bigfatmatt said:

Thanks, how should I size the starter for a 9.9kW 4 stroke petrol outboard? I assume it doesn’t need a 110Ah battery?

 

Anything above a couple of AAA batteries will do.

 

Assuming it starts normally then something like a 20Ah Golf Trolley battery would do.

If it is a difficult starter and you are going to be turning it over for minutes after minute than get a small car battery of around 80Ah would be more than enough.

[LadyG]

9 hours ago, bigfatmatt said:

 

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?

I bought a new AGM starter battery, cheap as chips. Plus three or four modern deep cycle AGM leisure batteries, total nominal 600ah. I have 550w solar and this does me seven months of the year, batteries are four years old and seem fine. 

I often switch the ancient 12v fridge off and on manually as it will drain the batteries, it's not a great thing, freezing too much, then needing defrosted, plus keeps one awake at night. Other than the fridge everything works fine three seasons. 

I would not bother about gels, no advantage on a narrow boat as far as I am aware. A good AGM starter battery eg Bosch will outlive everything else, they are designed for that one job and are rarely taken out of their comfort zone.

If you don't give your FLA proper maintenance they will die prematurely, so any minor saving wil be wiped out.

 

Edited May 15, 2023 by LadyG

[magnetman]

2 hours ago, bigfatmatt said:

 

Any recommendation on which LiFePO4 batteries and BMS to look at?

 

Should I also have an AGM to start the outboard and just keep that completely separate?

 

I've not bought consumer product lithium batteries. Mine are slightly unusual Lithium Titanate electric bus batteries with no electronics on them which are at the end of the day a bit of a gamble.

 

There must be some other posters on here who have used the consumer products available from companies such as Fogstar. I don't know how they work in reality and the tech is quite new so it probably is a risk. Warranty is of course interesting but the company might not exist in x yars so these are not necessarily valuable warranties like one would get with established lead acid battery manufacturers.