spare battery charging question (1 Viewer)

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Nov 14, 2022
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Hi, i bought a Burstner which had just 1 70AH AGM battery fitted with 120W solar panel. I have bought a 120AH to replace it to give a little more. I was going to sell the 70ah but just thinking maybe keep it but obviously cant connect in parallel as its a different size. Do i fit a dc-dc charger just for that 1 battery or get another solar panel just for that battery? Im thinking i could just let that be the wifes battery :giggle::unsure: for her hairdrier when off grid with a inverter as i have told her no way can she use the 120ah for that luxury. Any tips etc appreciated.
 

stuartholmes

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Hi, i bought a Burstner which had just 1 70AH AGM battery fitted with 120W solar panel. I have bought a 120AH to replace it to give a little more. I was going to sell the 70ah but just thinking maybe keep it but obviously cant connect in parallel as its a different size. Do i fit a dc-dc charger just for that 1 battery or get another solar panel just for that battery? Im thinking i could just let that be the wifes battery :giggle::unsure: for her hairdrier when off grid with a inverter as i have told her no way can she use the 120ah for that luxury. Any tips etc appreciated.
I don't know if it's actually possible but (as you wouldn't get a lot of £ for a used battery) I'd investigate a battery master from VanBitz to charge the 70 from the 120 so you can use it as suggested until replacing with a second 120 wired in parallel.
Then use the battery master to keep vehicle battery topped up while you're parked in the sun but not going anywhere.
 
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pappajohn

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I was going to sell the 70ah but just thinking maybe keep it but obviously cant connect in parallel as its a different
Assuming the van is new the battery will also be new.
Size, Ah etc doesn't matter, what does is age and chemistry but as yours are new and both AGM then it's perfectly acceptable to parallel them.

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Feb 16, 2020
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Flying in the face of the sage advice not to do this I was unaware of at the time, I did similar with a new 50ah battery that fell into my lap f.o.c. As far as I know I've had no problems. Off grid, or E.H.U., 220w panel changing both, and cab battery. DC charger when driving. My original battery was a Varta 95ah. À.G.M. It worked fine on 3 week trips around ,Scotland, and France, and Wales. When their cream crackered, I'll look at Lithiums. The solar controller can handle them, as also can the dc 2 dc charger.
Mike.
 
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Russdcycle
Nov 14, 2022
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They can't really be in parallel as charging would only go to 70ah. Both batteries need to be same ah to work efficiently. I already have solar running to hab and vehicle and starter motor charges them both while running. The 70ah is a third battery and I am wanting an individual solution for that. For everyone's info the mh is a 2014 the leisure battery is new the 70ah is about a year old
 
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Sep 3, 2012
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They can't really be in parallel as charging would only go to 70ah. Both batteries need to be same ah to work efficiently. I already have solar running to hab and vehicle and starter motor charges them both while running. The 70ah is a third battery and I am wanting an individual solution for that. For everyone's info the mh is a 2014 the leisure battery is new the 70ah is about a year old
Sorry but that's incorrect.the 70ah will Charge up to 70ah and the 110ah will charge to 110 ah. (y).
If you don't want to connect them then just run a battery master off the 110ah to the 70ah to keep it trickle charged but this will only happen when your 110ah is fully charged.you can then connect a 12 v take off to run a tv for example. (y)
 
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Russdcycle
Nov 14, 2022
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All the battery companies I have spoken to including 1 at the nec show advised against 2 different ah in parallel. They said the smaller ah one would overcharge. I am already using my solar controller which is dual to hab and vehicle so my only option would be parallel with the hab but 120ah connected to 70ah in parallel is deffo not advisable.

Screenshot_20230328_201337_Chrome.jpg
 
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stuartholmes

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All the battery companies I have spoken to including 1 at the nec show advised against 2 different ah in parallel. They said the smaller ah one would overcharge. I am already using my solar controller which is dual to hab and vehicle so my only option would be parallel with the hab but 120ah connected to 70ah in parallel is deffo not advisable.

View attachment 732741
I was going to ask whether you'd been speaking with qualified techytypes or just sales people but that's a good screenshot, thank you.
 
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