12 replies to this topic

[So Cal Adventurer]

Hey All

 

Loving my 2018 Hawk and this group!

 

I just got a CPAP and want to use it while traveling as well.

 

I've been contemplating the switch to 6v for some time, and just had an idea.

 

I'm a barebones type of guy and travel light.

 

I am currently running the (2) stock deep cycle 12v that came with the camper, with solar, furnace going, fridge, and fans, it keeps up, but definitely works. hard.

 

Soo....  Thinking of instead of REPLACING the 12v with the 6v, just ADDING the 6v in the front dinette storage area.  For a total of 4 batteries and basically unlimited power.

 

Is this something that can be done?  Mixing 6v and 12v?  My brain says if wired correctly it shouldn't matter.

 

Right now, I am running 350watts of solar through the victron system.

 

Thoughts?

[longhorn1]

Hey All

Loving my 2018 Hawk and this group!

I just got a CPAP and want to use it while traveling as well.

I've been contemplating the switch to 6v for some time, and just had an idea.

I'm a barebones type of guy and travel light.

I am currently running the (2) stock deep cycle 12v that came with the camper, with solar, furnace going, fridge, and fans, it keeps up, but definitely works. hard.

Soo.... Thinking of instead of REPLACING the 12v with the 6v, just ADDING the 6v in the front dinette storage area. For a total of 4 batteries and basically unlimited power.

Is this something that can be done? Mixing 6v and 12v? My brain says if wired correctly it shouldn't matter.

Right now, I am running 350watts of solar through the victron system.

Thoughts?

You shouldn't be mixing batteries. They need to be the same and purchased at the same time. We have had a 2014 Grandby with 2 batteries and 100 W solar on the roof. We have the 80L Dometic compressor fridge. I use a CPAP machine and we have never had an issue with power usage. I believe you are over thinking this. If you really have a concern purchase the Yeti Goal Zero 400 Lithium power pack and use the 12 volt plug. I purchase one as a back-up for home and to take as an extra source. With the 12 volt for my CPAP the usage was only 16% with 7 hours of usage. Get the 12-volt plug and you can re-charge while driving. I have there 100W solar panel that I can use. jd

[Wandering Sagebrush]

I think you would be better off going with 4 six volts in series/parallel, instead of two 12 volts in parallel with 2 six volts wired in series.

You’d have fewer batteries to take up space, they would have a similar charging profile, and probably larger capacity (ampere hours). Trojan makes true deep cycle AGM 6 volts. I suspect they’re pricy.

That said, you could mix the batteries in series parallel, but I believe you would be disappointed with the results.

[Jack]

You can mix the 12 V and 6 V batteries. You connect the 6 V batteries in series (the plus of one to the minus of the other, making a "12 V" battery pair) and then you connect all of the 12 V plus terminals together and all of the 12 V minus terminals together. When you connect the group to the camper wiring, connect to it to the plus terminal one one battery and the minus terminal on another battery. With 3 batteries in paralle, use the "end" batteries for the camper connection.

 

If the batteries are of differing ages (and to some extent brands), you pay a price in battery life. The greater the difference, the shorter the life. What happens is that the newer batteries will expend some energy "charging" the older batterie, which shortens their life.Mixing marine and deep cycle batteries will cost you even more on total battery life.

 

Two 6 V batteries in series are better than two 12 V batteries in parallel for the same power (amp-hours @12 V or watt-hours). Whether you have 6 V or 12 V batteries, they will take up the same space for the same power.

 

For 6 V, go for golf cart deep-cycle batteries. Marine type batteries just don't last as long - your cost will be less for deep cycle over the life of the batteries. We have two Fullriver 6 V batteries, which are as good as if not better than Trojans, but cost less.

 

If you have the money, go for a single 12 V lithium-ion battery.

Edited by Jack, 25 May 2019 - 08:08 PM.

[klahanie]

Soo....  Thinking of instead of REPLACING the 12v with the 6v, just ADDING the 6v in the front dinette storage area.  For a total of 4 batteries and basically unlimited power.

 

Is this something that can be done?  Mixing 6v and 12v?  My brain says if wired correctly it shouldn't matter.

...

 

Thoughts?

 

I did something similar, adding 2 more 12V batteries FLA to the 2 existing 12V agms. Later, I replaced the original 12V pair with 2 x 6V FLAs, which would be the same as your plan. So I'd say, yes it can be done. I wouldn't say "unlimited power" tho .

 

As I understand it, a problem can be, when connected and idle, the chemistry of the different battery types and ages connected together will tend to compete against each other and run themselves down. So I used a marine type battery selector switch between the two "battery banks", 1 = old, 2 = new(er).

 

When charging they were combined, 1+2. because the line voltage from the charge source (alternator or shore) was high enough that both banks charged satisfactorily. Can't say for your solar, tho.

 

When not in use, the banks were separated, 0.

 

Usually when discharging I used one bank at a time - more to keep a reserve than anything else.

[ckent323]

Why not buy a rechargeable CPAP battery and charge it back up during the day?  A good one will cost about $300 - $350. 

 

They are small enough to put in a briefcase or suitcase along with your clothes or whatever.  Serves as a backup at home in case of power loss.  You can recharge your laptop or cell phone from it as well.

 

Less hassle and more convenient than adding more heavy 12V batteries albeit for a bit more cost.

 

Craig

[ntsqd]

I would suggest keeping the battery banks isolated from each other unless charging them. A marine battery bank selector switch wired in parallel with a VSR/ACR will do this. You'll also need a good way to monitor both banks.

Even with this, they're going to need to be the same type (FLA's, AGM's, etc) so that the charging profiles are reasonably close.

[So Cal Adventurer]

Why not buy a rechargeable CPAP battery and charge it back up during the day? A good one will cost about $300 - $350.

They are small enough to put in a briefcase or suitcase along with your clothes or whatever. Serves as a backup at home in case of power loss. You can recharge your laptop or cell phone from it as well.

Less hassle and more convenient than adding more heavy 12V batteries albeit for a bit more cost.

Craig

That’s actually a damn good idea! Thank you!!

I’m new to the CPAP world and didn’t even know 12v operation was an option!

Thanks

[So Cal Adventurer]

You shouldn't be mixing batteries. They need to be the same and purchased at the same time. We have had a 2014 Grandby with 2 batteries and 100 W solar on the roof. We have the 80L Dometic compressor fridge. I use a CPAP machine and we have never had an issue with power usage. I believe you are over thinking this. If you really have a concern purchase the Yeti Goal Zero 400 Lithium power pack and use the 12 volt plug. I purchase one as a back-up for home and to take as an extra source. With the 12 volt for my CPAP the usage was only 16% with 7 hours of usage. Get the 12-volt plug and you can re-charge while driving. I have there 100W solar panel that I can use. jd

Excellent points!

Thank you!

[esimmers]

 

 

Two 6 V batteries in parallel are better than two 12 V batteries in series for the same power (amp-hours @12 V or watt-hours). Whether you have 6 V or 12 V batteries, they will take up the same space for the same power.

 

 

 

I think Jack meant to compare two 6 volt batteries in SERIES with two 12 volt batteries in parallel. Both choices would produce 12 volts.