extra battery

fitzy · Veteran Member

extra battery

woofta and precious · Senior Member

Hi Fitzy,
Maybe just add another battery to start with and see how you go.
I had 2x80 watt panels on my Jayco with a mppt regulator and 2x120ah agm's
Surprisingly it worked very well.
Before setting it up, I tested my wife's Resmed CPAP machine, complete with humidifier and heated hose to give the worse case scenario.
I used a small 33ah agm battery I have for the test, and it kept it going for 7 hours before I turned it off.
Checking the battery in the morning it was reading 12.4 volts after resting for an hour or so.
I guess it depends on what else you run from the batteries, as that was only running CPAP.
what is so good with a solar setup is that you can add to it as your needs change.
OTOH, I am certainly no expert!
Regards,
Brian

fitzy · Veteran Member

Thanks Brian I will do as you suggest and see how it goes

Regards

Jaahn · Guru

Hi

As I said in the other posting, a problem with having the two 120amp-hr batteries with a 20amp smart charger is that it will take 6 hrs to replace 50% of that capacity. You will not normally drive for that long. It was also said that the 150W panel only puts out <10 amps so the panel will not replace it in a day either. Basically the charging capacity both ways is too low for them both. Another 150W panel will only bring the current up to ~20 amps in good conditions.

So try it out and see what happens as far as the batteries go. If your use is low it may be OK, I have no experience with a CPAP. BUT if the batteries are gradually being discharged more than charged every day then you will kill them !! Put in some way of monitoring them for state of charge so you know what is happening.

Jaahn

Aus-Kiwi · Guru

Battery and add extra solar ..

JayDee · Guru

I am hesitant to install a new battery as It is said that if I add a new battery now it will automatically be reduced to the same capacity of my existing battery.It would be best to wait until the old battery dies and then add two brand new batteries.
We are getting along ok with just the one battery, but would like the extra power for when bush camping.

Can I have some thoughts from you guys re the above.
many thanks

jay&Dee

Tony Bev · Guru

JayDee wrote:
I am hesitant to install a new battery as It is said that if I add a new battery now it will automatically be reduced to the same capacity of my existing battery.It would be best to wait until the old battery dies and then add two brand new batteries.
We are getting along ok with just the one battery, but would like the extra power for when bush camping.

Can I have some thoughts from you guys re the above.
many thanks

jay&Dee

Hello JayDee

I had the same problem as yourself.

I had an original 100 AH GELL battery of unknown age and use.

I then fitted an extra newish 55 AH hybrid crank/deep cycle AGM battery, which I had laying around

To keep them on separate circuits, I used (2 off) four way switches.

One four way switch was to allow me to charge them one at a time

The second four way switch allowed me to use their power, one at a time

When I finally get two new batteries, I can either remove both the switches, or just set them to use both batteries, at the same time

Below is the link to the type of switch I used

http://www.ebay.com.au/itm/AQUATRACK-6-32V-300A-DUAL-BATTERY-ISOLATOR-KILL-SWITCH-Boat-Marine-Caravan-4x4-/190711404589?hash=item2c6749182d

PeterD · Guru

fitzy wrote:
I would now like to instal an additional exact same battery to run the Mrs. CPAP
machine when camped-out as it is getting very low on power by morning. My question is will my current
charger be big enough to charge the extra battery

This to me indicates your charger is not in use when you are "camped-out." Your charger will carry the load of your CPAP machine and there would be no discharge of your battery at all if it was being used. When you are on 240 V power your charger will be capable of providing 480 Ah of charge so it will be capable of charging a battery bank of over 300 Ah in 24 hours.

Your 150 W panel is capable of generating about 50 Ah of current if you can achieve 6 sun hours a day. Six sun hours per day represents excellent operation in the better parts of Oz. In Tasmania you are luck to get 2 - 4 sun hours per day. In Victoria you can do a bit better.

I reckon the first thing you need to fix first is the lack of solar power. I would suggest doubling the solar capacity, then worry about your battery. The reason for you getting low on power in the morning is you are not getting a fully charged battery on dull days.

-- Edited by PeterD on Tuesday 19th of April 2016 06:06:28 PM

-- Edited by PeterD on Tuesday 19th of April 2016 06:06:56 PM

in transit · Senior Member

There are 16 to 18 hours/day where the current flow is all one way (out of the battery). If you were able to get the battery charged to say 100AH capacity by the time the sun went down, you need to use no more than 50aH o/night which has to be shared between your lights, water pump, TV and of course the CPAP machine. If the fridge is compressor powered, or you have a hungry inverter the situation gets worse.

So it seems to me you have 2 problems to consider;
have you got enough aH to last o/night and will you get enough sunlight to recharge the battery the next day. Obviously when it is raining all day it doesn't matter how much solar capacity you have. In those conditions we start the motor and let the 40A DC-DC charger do some work , or we start looking for a caravan park.

JayDee · Guru

Tony E
Thanks mate I will check it out
Jay&Dee