Charger 29v bad for Water Pump?

[NorthwichTrader]

Hi,

Things are moving as slowly as they ever have with my self-fit-out.

I'm currently keeping my batteries charged by using a numax charger (24v). However, when it first starts charging, the voltage shoots up to 29v and I think it then floats around 26/27 (I forget which)? Does anyone know whether this, apart from driving the water pump at a million miles an hour, cause it any long term damage?

Does this happen when you charge your batteries via a combi unit?

Many thanks,

Stuart

[by'eck]

All boat electrics should be able to cope with these voltage peaks as a result of multi-stage charging.

 

Above 15, or 30 volts (for 24 volt system) precautions need to be taken. For example when setiing charger in an equalise mode (nominally 15.5 volts) all electrical loads apart from batteries of course, should be switched off for the duration.

[NorthwichTrader]

Many thanks for that, that's extremely reassuring. I've been meaning to ask for such a long time! Brilliant! ?

[OldGoat]

All boat electrics should be able to cope with these voltage peaks as a result of multi-stage charging.

 

Above 15, or 30 volts (for 24 volt system) precautions need to be taken. For example when setiing charger in an equalise mode (nominally 15.5 volts) all electrical loads apart from batteries of course, should be switched off for the duration.

 

 

Many thanks for that, that's extremely reassuring. I've been meaning to ask for such a long time! Brilliant!

 

'Funny' you should ask that - I've just being going through that whole process.

A Very Nice Man in Wolverhampton came up with what I thought was a throwaway line:-

"Of course you could always put a diode (or two) in series with the distribution from the batteries"

 

? Oh yeah?? - but then I thought - well that's not impossible or expensive; just have a switch around the diodes for when you've stopped charging.

A bit of a faff though.

Fine for most domestics and even a small inverter and 25 / 50 amp diodes aren't expensive.

 

Think on't ....

 

I wasn't going to do it - but perhaps now stimulated - I might.

Edited November 24, 2015 by OldGoat

[nicknorman]

29v is pretty much the optimum bulk charge voltage. 26.5v is the optimum float voltage. Both those assuming batteries at room temperature, and wet lead acid type batteries.

[nicknorman]

For example when setiing charger in an equalise mode (nominally 15.5 volts) all electrical loads apart from batteries of course, should be switched off for the duration.

It depends. For example our LEDs are fine up to 30v ( 12v system so equalising at 15.5v). Fridge is a 12-24v model so that should be fine. Water pumps probably go a bit fast but with the occasional and intermittent use they are not going to expire at 15.5v. In fact I think the list of things likely to suffer is shorter than the list not likely to suffer. On the former would be any incandescent light bulbs, the Mikuni glow plug and .... can't think of anything else!

[bottle]

You are both correct.

 

The OP has a 24v system so if carrying out an equalisation charge that would be more than 30v so even LEDs rated to 30v may complain.

[nicknorman]

You are both correct.

 

The OP has a 24v system so if carrying out an equalisation charge that would be more than 30v so even LEDs rated to 30v may complain.

True!

[by'eck]

It depends. For example our LEDs are fine up to 30v ( 12v system so equalising at 15.5v). Fridge is a 12-24v model so that should be fine. Water pumps probably go a bit fast but with the occasional and intermittent use they are not going to expire at 15.5v. In fact I think the list of things likely to suffer is shorter than the list not likely to suffer. On the former would be any incandescent light bulbs, the Mikuni glow plug and .... can't think of anything else!

 

Of course Nick, but turning everything off before running a true equalise charge on the batteries (achieved in my case by operating a single isolator) is so much easier and conforms to manufacturers advice.

 

In fact following advice I think from yourself I don't even fire up my Mikuni when chargers are in absorb mode. Still using the original glow plug.

[Hairy Animal]

Thanks for that note about Mikuni heaters Richard. Our restoration will include a 24V system for the fridge/freezer, diesel hot water heater and Mikuni hot air heater, so I shall either ensure the Mikuni isn't switched on when the batteries are on charge, or better still design a regulator to maintain 24V so that we can stay warm even when charging.

[ditchcrawler]

Many thanks for that, that's extremely reassuring. I've been meaning to ask for such a long time! Brilliant!

I regularly charge at 29.5 volts but I don't expect the pump runs that often at that voltage as I am driving the boat, it is possible that Diana is filling the kettle

[nicknorman]

Thanks for that note about Mikuni heaters Richard. Our restoration will include a 24V system for the fridge/freezer, diesel hot water heater and Mikuni hot air heater, so I shall either ensure the Mikuni isn't switched on when the batteries are on charge, or better still design a regulator to maintain 24V so that we can stay warm even when charging.

The 24v version of the Mikuni still uses 12v glow plugs I think, and thus presumably has some sort of voltage reduction built in. Anyway, the glow plug is only powered for the first minute or two of light-up so you would be safe to put the charger on after that, so long at the Mikuni doesn't start cycling off and on.

[NorthwichTrader]

Thanks SO much, chaps, never disappointed on here!

Can I ask how easy it would be, or whether it's even possible, to put something inline on the water pump that restricts the voltage to it to say 24/25 v?

I only ask because it's a tad noisy, even at 25 v, but at 29 v is giving us all a nervous disposition!

If it's complicated I'll just buy 3 sets of ear plugs!

[ditchcrawler]

Thanks SO much, chaps, never disappointed on here!

Can I ask how easy it would be, or whether it's even possible, to put something inline on the water pump that restricts the voltage to it to say 24/25 v?

I only ask because it's a tad noisy, even at 25 v, but at 29 v is giving us all a nervous disposition!

If it's complicated I'll just buy 3 sets of ear plugs!

For how long each day are you poking 29 volts into the batteries and for how long is the pump running for in that time.

[NorthwichTrader]

For how long each day are you poking 29 volts into the batteries and for how long is the pump running for in that time.

I'm typically charging the batteries overnight, and switching the charger off in the morning. However, my wife leaves for work at 6am so, despite the best intentions, we do get a major wake-up call!

Also, every time the pump runs, it chucks the charger back into 29v for 30 secs or so, which means the second cycle of the pump, even if it was started in the float mode, is at 29v.

[nicknorman]

Perhaps the answer is not to worry about the voltage at the pump, but rather to try to improve the sound insulation of the pump. Anything that couples the pump body directly to the boat's structure is likely to transmit the noise. Make sure the pump is flexibly mounted. You might also experiment with short lengths of hose to connect the pump to the plumbing. Do you have an accumulator to absorb the pump's pulses?

[Hairy Animal]

It might be a silly question but the pump is definitely rated for (nominally) 24V isn't it?

[swift1894]

All boat electrics should be able to cope with these voltage peaks as a result of multi-stage charging.

 

Above 15, or 30 volts (for 24 volt system) precautions need to be taken. For example when setiing charger in an equalise mode (nominally 15.5 volts) all electrical loads apart from batteries of course, should be switched off for the duration.

I presume you mean all 12v/24v loads not 230v.

[bottle]

I would expect the 12/24v equipment to include the inverter and so by inference all 240v ac. (the inverter would probably shut down because of 'over voltage')

 

but

 

Any 240v ac directly connected to a shoreline/generator would be available.

[by'eck]

I presume you mean all 12v/24v loads not 230v.

 

Yes if you check the thread title and every post you will see they all refer to DC system voltages.

 

ETA: apart from one above that crossed with my post.

Edited November 25, 2015 by by'eck

[NorthwichTrader]

Yes, Nick, there are plenty of improvements I can make re the sound proofing!

I will look into some proper engine mounts too...saw this on eBay (291516045186 - sorry, can't link on my phone), so might give them a try!

 

Thanks to everyone, I'm reassured to know it won't knacker the pump, which is 24v I hasten to add!

[Hairy Animal]

The diode(s) suggested earlier in this thread might be a good idea if the pump is unhappy with the higher charging voltage. On eBay, a seller, macus55_123, has 10 HFA08TB120PBF diodes on offer that have no bids at the moment. These can take 8A continuously and 130A peak, so should cope with start-up loads. They will drop the supply by 3.3V irrespective of the voltage, so if the batteries are down to 24V you'll only be getting 20.7V to the pump, but at 29V you'll get a more reasonable 25.7V. They'd need a heatsink; any old lump of metal would probably do but it will be at the same voltage as one side of the diode, therefore 24V ish if fitted in the +ve feed to the pump. These diodes normally sell at £2 - £3 each so the current eBay price is a bargain.

[GUMPY]

The voltage drop over a diode varies with the current drawn through it.

I will say no more

[swift1894]

Yes if you check the thread title and every post you will see they all refer to DC system voltages.

 

ETA: apart from one above that crossed with my post.

Thought so but just checking.? Edited November 25, 2015 by swift1894

[Hairy Animal]

The voltage drop over a diode varies with the current drawn through it.

I will say no more

It will only vary very slightly with current, a few mV probably

The quoted forward voltage for the diodes is 3.3V and that's what it will be for currents from 100mA to 8A give or take a mV or so.