Solar and battery changing question please.

Apr 9, 2018
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Worcestershire
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53,271
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Burstner Harmony 745
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March 2018
We about to spend a week at a rally using only 100w of solar to supply our leisure battery, and the starter battery via a Battery Master.
have no idea how much power we will need so plan to keep electrical usage to a minimum.

The leisure battery is an AGM type but I do have a spare wet cell leisure battery at home which I may stick in the boot of the toad just in case.

Q1. Can I just swap an AGM and wet cell as regards the on-board charger, solar controller and the engine charge from the alternator? Are they interchangeable?
Q2. If I did want to swap in the wet cell battery would I need to disable anything on the solar side whilst I did it? I realise I would have to be careful about shorting out the leads but will I cook the solar controller or main EBL if I just disconnected the AGM and connected the wet cell?

TIA.
 

Lenny HB

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Oct 18, 2007
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You will need to change the solar regulator setting as the AGM setting charges at 14.7v too high for a wet cell.

Also you need to disconnect the solar panels from the regulator while swapping batteries. This is because the battery need to be connected to the regulator first, then the panels.

Alternator charging should be OK.
 
May 3, 2021
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80,868
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AutoTrail F70
A really good idea is to have a power audit, it can be as simple as noting down everything that draws 12v power and totting it all up.
If you have an inverter that adds complexity to the matter as you have the drain of the device plus the inefficiency of the inverter.

Once you have an idea how many amp hours you are likely to be using on average, you can work out what you would need to support that and if your batter bank is sufficient, and then add back in any form of recharge mechanism such as solar.

I hope you will excuse the impertinence of posting a link, but this is a good east read: https://www.parkedinparadise.com/calculate-electricity/

In my limited experience, most common or garden solar chargers are not overly fussed about the type of battery until you start using exotic stuff like lithium or gel cells, check your manual for options, but I‘d hazard a guess that unless you are very very precious about your AGM it will simply replace the wet cell.

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OP
David and Sally
Apr 9, 2018
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Worcestershire
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Burstner Harmony 745
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March 2018
You will need to change the solar regulator setting as the AGM setting charges at 14.7v too high for a wet cell.

Also you need to disconnect the solar panels from the regulator while swapping batteries. This is because the battery need to be connected to the regulator first, then the panels.

Alternator charging should be OK.
Thanks.
I’ll check tomorrow to see if the regulator has different settings.
A most helpful answer. Cheers
 
Aug 7, 2019
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I'm a newbie
Following on from the Op's questions, a more basic one. We're all off to the Topsham rally for a week without EHU. So an impossible question to answer I know but based on the fact the I've got a fully charged leisure battery and 100w solar panel, with careful usage / monitoring will I have enough juice to get me through the week bearing in mind that a lot of the time we'll be away from the van not using the 12v and while we're away the solar will be re-charging the leisure battery.
Maybe you can answer my conundrum based on your experiences of going off grid for a week.

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Lenny HB

LIFE MEMBER
Oct 18, 2007
30,772
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On the coast in West Sussex
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658
MH
Hymer B678 Dynamic Line
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Since 2008 & many years tugging
Following on from the Op's questions, a more basic one. We're all off to the Topsham rally for a week without EHU. So an impossible question to answer I know but based on the fact the I've got a fully charged leisure battery and 100w solar panel, with careful usage / monitoring will I have enough juice to get me through the week bearing in mind that a lot of the time we'll be away from the van not using the 12v and while we're away the solar will be re-charging the leisure battery.
Maybe you can answer my conundrum based on your experiences of going off grid for a week.
Shouldnt be a problem at this time of year if you are careful, may struggle if you get a few days without sun.
 
May 6, 2021
80
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Kent, UK
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80,971
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Adria twin supreme
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2001
Following on from the Op's questions, a more basic one. We're all off to the Topsham rally for a week without EHU. So an impossible question to answer I know but based on the fact the I've got a fully charged leisure battery and 100w solar panel, with careful usage / monitoring will I have enough juice to get me through the week bearing in mind that a lot of the time we'll be away from the van not using the 12v and while we're away the solar will be re-charging the leisure battery.
Maybe you can answer my conundrum based on your experiences of going off grid for a week.
It all depends on what is running on the 12v system. For example if you have a compressor fridge then it will probably not last a week with only 100W panel. Even evaporated fridges use some electric with control circuit's. Water pumps take a lot current draw when in use. Do you watch a TV at night. One way to save battery use is to use the garden solar lights. We put them in jars, use at night and put out to charge during the day.
If your solar controller can take it you can always get a second 100w panel, put it outside then van and plug it into the controller as a second supply. We had two panels setup on pull out legs as a temporary solution.
 
Jan 19, 2014
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We managed for 2 weeks with a free standing 40w panel in Scotland in August 2014. All depends on what you use.

40w free standing is probably equal to 80w flat mind 🤔

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May 6, 2021
80
43
Kent, UK
Funster No
80,971
MH
Adria twin supreme
Exp
2001
We managed for 2 weeks with a free standing 40w panel in Scotland in August 2014. All depends on what you use.

40w free standing is probably equal to 80w flat mind 🤔
That is good, like you say depends on use. If all you do is turn on a few led lights at night an bit of pump use then it will probably be ok. Also depends on your battery capacity, type of battery and condition of battery. You can also drain your battery down below 50% and when charged say its still ok but you will have damaged it and will never get the full 100% charge again. If you keep topping it up you will never know. In end its an impossible question to answer. Like you say, you was ok for a week. We have a compressor fridge which is standard on new Adria vans and will only last about two days on 100aH battery
 
Dec 6, 2011
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South Wales
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We have just done 6 nights with no problem on 140w panel and 120ah battery, and there was no sun and very low cloud for a day and a half.
The biggest consumer of battery seemed to be the heater blower as it was quite cold on 3 of the nights.
So when the blow heating is not needed and reasonably sunny I would expect to have few problems with the leisure supply.
 
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