Leisure battery question

[Howard B]

A question for those who understand leisure battery systems better than I do.

Following a minor water leak discovered a few weeks ago, I have been running a small 23w dehumidifier from my inverter overnight. Up until yesterday all was running fine. The batteries are connected to a 100w solar panel.

However when I opened the van this morning, the inverter was not powered up. When I checked the battery status on the control panel, it was showing 11.5 v. the dehumidifier was the only thing running so I assume that was the source of the drain, however it has been fine up to now.

I took the van for a 30 mile drive which upped the voltage to 12.2v & its now plugged into in the EHU which has taken the voltage to 12.5 v.

I have two batteries in parallel one is a Varta 85AH and the other is the original Adria fitted battery which I can’t see any markings showing the AH but assume is @ 60 or 70AH. Also assume the batteries are 4 ½ years old.

So, my question is, how do I know if the batteries need replacing other than waiting to see if they discharge again?

 

[autorouter]

I hope you realise that the voltage of a battery while it is being charged has very little relation to the state of charge. A battery bank of 150Ah capacity will take 8 hours minimum to recharge, and that's with a 20A intelligent charger. The battery voltage will gradually creep up to 14.4V over a few hours, stay at 14.4V for a few hours, then drop to about 13.6V when charging has finished and it goes into float mode.

Degraded batteries often behave exactly like a good battery, but with reduced capacity. So your 150Ah nominal capacity might really only be half of that. The only way to tell is to discharge them into a known load, and see how long they last.

From your figures it's not looking good. I don't know the inverter wattage, but even if it's a big one it won't be wasting more than 2 or 3 amps. Combined with the dehumidifier (about 2 amps) that's 5 amps consumption, it should in theory last more like 30 hours. Is it possible they weren't fully charged to begin with?

 

[Howard B]

I don’t know the battery status over the last couple of weeks..( lesson learned). I’ll leave it on the EHU for a day or so & see how it goes I thought the solar wiyluld have kept it topped up, but maybe not.

 

[Minxy]

Why are you running the dehumidifier at night? Much better IMV to do it during the day when the warmer air will hold more moisture and of course use it only on hook-up. No point in draining your batteries if you don't need to.

 

[TerryL]

Best you'll get out of a 100w solar panel is around 5 amps which is what your system appears to be pulling out, so whilst the sun is shining you're covered. However when the sun isn't shining you've got a permanent 5amp drain so assuming 50% (useable capacity) of your, say, 160 ah batteries, you've got 80ah/5a = 16 hours so assuming my maths is correct I think your batteries are doing okay. But if you let them drop below 50% capacity then you're going to start causing them problems. 11.2 volts, read with no load and after letting the batteries settle for at least half an hour, is just about completely flat.

(I'm surprised the humidifier was still running if the inverter wasn't? Or have I misunderstood that?)

If you're lucky and the recharge goes okay - better with an "intelligent" charger - you may have got away with it although I'd guess you've probably reduced their remaining life. As you say, the only way to find out is to get them fully charged again, monitor them and see how long they retain the charge. Meanwhile I'd try and find some other way of dehumidifying if it's still necessary.

Oh yes, and start putting pennies into a piggybank............................!

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[Howard B]

Why are you running the dehumidifier at night? Much better IMV to do it during the day when the warmer air will hold more moisture and of course use it only on hook-up. No point in draining your batteries if you don't need to.

I realise that now.

 

[Minxy]

I realise that now.

We all have to learn how to use things in the best way ... you ought to see some of the things that 'experienced' motorhomers admit to who should know better.

 

[Howard B]

Best you'll get out of a 100w solar panel is around 5 amps which is what your system appears to be pulling out, so whilst the sun is shining you're covered. However when the sun isn't shining you've got a permanent 5amp drain so assuming 50% (useable capacity) of your, say, 160 ah batteries, you've got 80ah/5a = 16 hours so assuming my maths is correct I think your batteries are doing okay. But if you let them drop below 50% capacity then you're going to start causing them problems. 11.2 volts, read with no load and after letting the batteries settle for at least half an hour, is just about completely flat.

(I'm surprised the humidifier was still running if the inverter wasn't? Or have I misunderstood that?)

If you're lucky and the recharge goes okay - better with an "intelligent" charger - you may have got away with it although I'd guess you've probably reduced their remaining life. As you say, the only way to find out is to get them fully charged again, monitor them and see how long they retain the charge. Meanwhile I'd try and find some other way of dehumidifying if it's still necessary.

Oh yes, and start putting pennies into a piggybank............................!

The dehumidifier wasnt working either. I still need to use it but will run on mains from now on. Been looking at the price of batteries at Battery Megastore. These seem a reasonable price, but when you go into the spec its states for engine start. https://www.batterymegastore.co.uk/product/hankook-sa58020-agm-leisure-battery-uk-part-code-110/

 

[Minxy]

There are a few threads on the forum about batteries and many are happy with AGM but I, like a lot of others, have gels as they appear to have a much better lifespan and can be discharged lower without serous effect (down to 20%), have a shuftie at Tayna's 'Sonnenschein 65' ones.

Lenny HB ... one of your favourite subjects ... AGM batteries!

 

[Howard B]

have a shuftie at Tayna's 'Sonnenschein 65' ones.

££££

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[Minxy]

££££

Not that much more than the ones you're looking at bearing in mind that you gain by getting more usable capacity for when you need it, plus they are likely to last a LOT longer - I think if you sign up for the Tayna newsletter you might get a discount code sent to you.

 

[Howard B]

I take it I can use both AGM or Gel with this Electrical Management panel (EBL208 SG)

 

[TheBig1]

I really would advise you against AGM for typical motorhome usage. They just don't last very longand for the cost,not worth the hassle. Simple wet lead acid are cheap and effective and will get you 4 or 5 years typically. Gels are more expensive but will last probably 8 years and allow lower discharge states without damage. It all depends on your budget and plans for the van

 

[Howard B]

My handbook states not to use lead acid, so its either AGM or Gel.

 

[Minxy]

I take it I can use both AGM or Gel with this Electrical Management panel (EBL208 SG)

Yup.

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[Minxy]

My handbook states not to use lead acid, so its either AGM or Gel.

We had the same as you, only AGM or gel. The dealer we bought our last PVC from (Globecar Campscout) from put a pair of matched lead acid ones in as we paid for a second matched leisure battery, I went nuts as it should have been the same as the existing gel so they paid to have them both changed to gels.

Have you got an 'all electric fridge? If so the gels will be much better.

 

[Howard B]

3 way fridge

 

[Minxy]

3 way fridge

Okay that's a bonus, but I'd still go for the gels, fit and forget (so long as you look after them properly of course).

 

[Howard B]

Due to size constraints, I cant get two Sonnenschein to fit and give me more than @ 120AH ( I can only go to 310mm length on one battery & 360mm on the other). So a quick search reveals I can get two Exide Gel at 85AH and a 56AH for @ £334 or two Varta AGM at 95AH & 60AH for @£295.

 

[Pausim]

I am having a bit of trouble believing that there is such a thing as a 23w dehumidifier. Am I missing something? I would welcome being put straight on this.

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[Howard B]

I am having a bit of trouble believing that there is such a thing as a 23w dehumidifier. Am I missing something? I would welcome being put straight on this.

Here you go Amazon product ASIN B00VJ1EIMA

 

[Minxy]

Due to size constraints, I cant get two Sonnenschein to fit and give me more than @ 120AH ( I can only go to 310mm length on one battery & 360mm on the other). So a quick search reveals I can get two or two Varta AGM at 95AH & 60AH for @£295.

Looking at your figures and restrictions:

• Sonnerschein Gel: 78ah & 56ah = 134ah (usable capacity 107ah) @ £289
• Exide Gel: 85AH & 56AH = 141ah (usable capacity 112ah) @ £334
• Varta AGM: 95AH & 60AH = 155ah (usable capacity 108ah) @ £295

Is the extra 1ah or 5ah worth the extra cost?

NB Sonnerschein are made by Exide:

 

[Howard B]

Batteries were hooked up to EHU all night, only sitting at 12.2 V.

 

[Bessy765]

If it only require 9 volts dc why not use a dropper to go from 12 volts to 9 volts. This will cut out the losses turning 12 volts d.c. to 240 volts a.c. Back down to 9 volts d.c. probably around 20%.

 

[Howard B]

If it only require 9 volts dc why not use a dropper to go from 12 volts to 9 volts. This will cut out the losses turning 12 volts d.c. to 240 volts a.c. Back down to 9 volts d.c. probably around 20%.

You have lost me

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[TerryL]

A dropper is a "technical" term for a device that reduces voltage - much more efficient than using the inverter but of course there's the cost. Another nice gadget to have but in reality how often are you going to use it considering you've almost sorted your original problem?

 

[Howard B]

I don't know where you got my need to get a 9v supply.

 

[TerryL]

I don't know where you got my need to get a 9v supply.

It's in the specs of the device on the Amazon site you linked.

 

[autorouter]

Batteries were hooked up to EHU all night, only sitting at 12.2 V.

Are you sure the EHU charger is working? It should charge to over 13V, unless your batteries have a really rare serious fault.

 

[Howard B]

OK so I had a quick look at the fuses on the Electrobloc EBL208 SG and the 20a fuse for the internal charging has been pulled. I can only assume ( or hope) that is because the PWM solar charger has been connected directly to the batteries and not via the Solar connector on the Electrobloc.
So from what I can work out, the Solar panel feeds into the Solar charger which is then attached directly to the batteries. I assume the two cables comming from the rear of the battery with the red & yellow plactic markers in the picture come direct from the Solar controller.

On the bottom side of the terminal Fuse 7 ( Internal charging) I have 14.26v which I assume is from the EHU. The top side is 12.69 which is current battery voltage. So I guess when I checked this morning it was low because the EHU wasnt doing anything . This evening it was showing 12.7 because the solar had been pulling in UV all day. it has dropped slightly now due to being dusk.
If I put the fuse in I guess I will/ could damage the UV panel/ controller. Any thoughts or should I move this last bit to to the Solar section for more ideas on how to sort this.
Thanks H

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