Adding extra batteries

Submitted: Saturday, Apr 01, 2017 at 07:28
ThreadID: 134574 Views:3744 Replies:7 FollowUps:13
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I have a caravan with 2 x 110 amp agm batteries about 3 years old. They appear to work well but i would like to add one or two additional batteries to increase the power reserve.

The van has a 230 litre vitrifugo fridge freezer,that from the website uses 65 w (5.4amps) but there is no reference to cycle time.

Can i add new batteries identical to the originals (that are 3 yrs old ) without ill effects to the new batteries ?

Thankyou for any advice.
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Reply By: Sand Man (SA) - Saturday, Apr 01, 2017 at 08:09

Saturday, Apr 01, 2017 at 08:09
Yes you can add extra batteries.
With all connected in parallel, the integrity of the battery bank will be as good as the "worst" battery in the bank. With the two current batteries 3 years old, you may like to consider "how long before one of the existing batteries starts to play up", thus degrading the whole bank.
With four 110 Ah AGM's, you would be carrying one hell of a lot of weight.
Maybe it is time for you to consider investment in Lifepo4 lithium batteries, if you really need more capacity. These batteries are much lighter for an equivalent capacity, although they are significantly more expensive to purchase.
Or better still, maybe consider that a 220Ah capacity battery bank is good enough to suit your needs, especially if supported by solar panels, or 240v charging.
I have two 100Ah batteries in my van to support a 70l Waeco compressor fridge, plus the 40l portable Engel I plug into the van supply when at camp. The two batteries are maintained by a 120w solar panel when free camping and I have not run low on power yet.

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Follow Up By: Tim F3 - Saturday, Apr 01, 2017 at 08:20

Saturday, Apr 01, 2017 at 08:20
Bill thankyou for your reply , i have 300 watts of solar on the roof.

The fridge runs the 2 x 110 amp batteries down to 11.9 to 12.1v overnight (it is 230litres ).

The solar tops the batteries back up if there is good sun but will not if the sun is poor.

This is why i thought to increase battery and also solar capacity.
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Follow Up By: The Bantam - Sunday, Apr 02, 2017 at 07:49

Sunday, Apr 02, 2017 at 07:49
your #1 problem is insufficient solar capacity ..... the first thing you need to spend on is sufficient solar capacity to fully charge the batteries every day, even if the sun is not strong.

No matter how much battery capacity you have ...... it won't help you if you have insufficient charging capacity.

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Reply By: HKB Electronics - Saturday, Apr 01, 2017 at 10:06

Saturday, Apr 01, 2017 at 10:06
Your fridge is consuming a lot of power it would seem, adding extra batteries gives you more capacity but as your already running your batteries down to 40% SOC the question would be do you have enough solar power to charge the extra batteries?

If you find you can charge your present batteries by say lunch time then adding extra batteries could be your answer, if it is presently taking all day to charge your existing batteries then adding others is pointless unless you also increase your solar output.


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Follow Up By: IvanTheTerrible - Saturday, Apr 01, 2017 at 10:11

Saturday, Apr 01, 2017 at 10:11
Listen to this guy. He knows what he's talking about
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Follow Up By: RMD - Saturday, Apr 01, 2017 at 17:53

Saturday, Apr 01, 2017 at 17:53
In addition to HBK which I agree with, If two batteries that size are not lasting all night and the voltage is so low in the morning, it would seem the batteries can't store what is being delivered to them, ie not able to hold sufficient charge and are below their rated capacity OR they aren't being FULLY charged each day even though the voltage is "all good" by lunch according to the voltmeter.
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Reply By: pop2jocem - Saturday, Apr 01, 2017 at 11:41

Saturday, Apr 01, 2017 at 11:41
Just something to consider. As you have already noted, the existing solar you have works great to re-charge what you have. Adding extra batteries may need additional solar capacity which is fine. The problem could raise it's head when the sun isn't shining, that regardless of the amount of solar you have they won't do much to help without some sunlight.
You may be one that wouldn't use a generator under any circumstances but they do work day or night sunny or cloudy.

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Follow Up By: Tim F3 - Saturday, Apr 01, 2017 at 12:18

Saturday, Apr 01, 2017 at 12:18
Pop thankyou for your reply , you are correct and i will consider a generator .

I was at congo national park recently near moruya , their rules are that generators may be used between 10 am to 12 pm and 2 pm to 4pm just out of interest , so i did use a small honda generator on one day.
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Follow Up By: MEMBER - Darian, SA - Saturday, Apr 01, 2017 at 19:30

Saturday, Apr 01, 2017 at 19:30
Yep re the gennie comment above - given that you have that big power hungry fridge, and a copious yet semi-reliable solar supply (could be overcast), a gennie is certainly indicated. A few points that seem valid from my experience (but I'm not a qualified technician): 1. Letting batteries get down around the 12V level and under is bad for their health (and your wallet). 2. Adding a portable solar panel to your setup is worth can often catch sun early and late in the day that the fixed solar panels aren't exposed to. Adding another deep cycle would help (as mentioned, as long as it can get charged), but also as mentioned, make sure you can accommodate the extra weight in that locker. 3. A small, inverter generator for topping up the batteries is worthwhile (being mains quality power, it can be used for running other 'delicate' appliances too...and might help at home when the power goes it does here in SA.. :-)...a 1k gennie might weigh 12-13kg.
For the record...I have 3 x 100Ah deep cycles in the van, a 150L Vitrifrigo 2 door, 2 x 100w panels on the roof, a 100w folding portable solar kit and a 2k inverter gennie...(so when camped out, monitoring of incoming power and the state of battery charge never ends) ! True that there are many camps/places where you can't run a gennie....but if you need power and can run the gennie, you might well save those expensive batteries.
FollowupID: 879717

Reply By: Member - Rod N (QLD) - Saturday, Apr 01, 2017 at 12:24

Saturday, Apr 01, 2017 at 12:24
In addition to the electrical side of things you have to consider the weight of the batteries and your vans payload. You might be able to run your fridge for longer with extra batteries but will have to compensate for the weight by leaving you slabs of beer at home.
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Follow Up By: RMD - Saturday, Apr 01, 2017 at 17:57

Saturday, Apr 01, 2017 at 17:57
2 x 120 ah additional batteries is around 70 litres of grog too. A bit less if stubbies.
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Follow Up By: Tim F3 - Saturday, Apr 01, 2017 at 20:25

Saturday, Apr 01, 2017 at 20:25
Can put additional batteries in the back of the cruiser so accomodate the necessary beveradge in the van fridge ....or ....just add one extra battery or use a
Btw the van has a capacity of 620 kg of load items..should be ok..
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Reply By: The Bantam - Sunday, Apr 02, 2017 at 07:56

Sunday, Apr 02, 2017 at 07:56
As has been mentioned above, more solar capacity is an issue.

In addition .... your batteries have some age and if they have been continually deep discharged and not fully recharged, they may be functioning well below capacity.

Also, batteries in a poor state of health can have poor charge acceptance ..... no matter what charger you use of it's capacity they may be slow to charge.

you should have your existing batteries load tested to determine their state of efficiency.

AnswerID: 609844

Follow Up By: pop2jocem - Sunday, Apr 02, 2017 at 10:45

Sunday, Apr 02, 2017 at 10:45
Regardless of whether you add extra solar, a genny or use 240v mains as a charging method, I would have your existing batteries load tested as Bantam has said before connecting extra new batteries and risk shortening their life span.

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Follow Up By: Tim F3 - Sunday, Apr 02, 2017 at 10:51

Sunday, Apr 02, 2017 at 10:51
Bantam thankyou for your reply , its a good idea will get it done this week.
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Reply By: Member - McLaren3030 - Sunday, Apr 02, 2017 at 11:20

Sunday, Apr 02, 2017 at 11:20
As a few people have already mentioned, it sounds like your existing batteries are on the way out. Deep Cycle batteries do not last forever, and while three years sounds like a long time for batteries (most only have a 2 year warranty), it depends on how many cycles they have been through. Deep Cycle Battery efficiency is dependent on the number of charging cycles. So even if your batteries are three years old, if they have only had a small number of cycles, then they should still be OK providing they have been kept charged, warm & dry. Getting them load tested would be a good place to start, & if found to be below par, then replacement batteries would be indicated. Adding more batteries to a system that is already compromised will not make much difference.

Increasing your solar charging capacity will definitely help. Even if there is little sunlight, more panels = more charge.

As stated by someone else, Lithium Iron Phosphate batteries are much lighter and will last up to 10 times longer (charging cycles, not years), however they are much more expensive. You will also most likely need to change the charging system in your van if you change over to these batteries. Another expense. Are they worth all the added expense? That is a question only you can answer, as it depends on your financial status. These batteries will last up to 10 times longer, but cost around 10 times as much. ($230 for 120 amp AGM Vs $2,300 for 120 amp LipePhos, plus around another $2,000 for a DC to DC Charger. Having said that, If I could afford, I would put in a LiPePhos system tomorrow. Saves around half the weight of AGM, plus lasts much longer.


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Follow Up By: PhilD - Sunday, Apr 02, 2017 at 20:37

Sunday, Apr 02, 2017 at 20:37
Macca, there are cheaper ways than that to put Lithium in. If you go to somebody like EV Works and buy the 3.2 volt cells, the cost is about $7.20 per amp hour, plus connectors, battery monitoring, relay, and appropriate chargers. So, 120 Ahr will be $864, plus the other bits. They recommend charging the Winston cells at 14.2 volts so you need an appropriate charger. A Sterling BcDc charger will set you back around $600-700, so it will be a lot cheaper than the figures you have used. I have a 400 Ahr pack I charge at 100 amps from my alternator/cranking battery and the system is only 56 kgs compared to over 200 kgs if I had the same capacity in AGM batteries, and a much smaller footprint. There are some crazy prices being charged for lithium at present, due to the way the systems are being packaged for those not wanting to build their own system.
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Follow Up By: The Bantam - Saturday, Apr 08, 2017 at 13:53

Saturday, Apr 08, 2017 at 13:53
I keep hearing this AGM comparison .... and AGM....AGM....AGM.

Serioulsy ....... there are very few situations that actually require AGM or where AGM has any specific advantage.

A lot of sellers will offer nothing but AGM .... simply because they do not have the ability to economically freight wet cell batteries .... AGM can be shipped in general freight.... wet cell batteries can not.

You can save yourself a lot of cost by rejecting the assumption that AGM is best ...... in many of the commercial high intesity applications AGM is not the prefered option and has no advantage.

Most golf buggies and small electric vehicles use conventional screw top wet cell batteries and in the market "Trojan" dominates.

Many remote area and off grid installations use either screw top batteries or sealed maintenence free batteries. ..... because they will stand the hammering better than AGM.

Yes a lot of modern telecommunicaton installations particularly small ones are using AGM .... mostly because of workplace saftey and freight issues more than anything else.

You may wish to avoid the issues of maintenance and go for a sealed maintenance free battery, that will have most of the advantages of AGM but at 1/2 to 2/3 the cost ..... AND they will generally be more temperature tollerant than AGM and tolerate higher charge rates.

While you are at it look at AGM manufacturer spec sheets and the recommended operating temperature range is quite narrow.

If you have AGM because it does not require ventilation ...... think again ..... ALL responsible AGM battery sellers and ALL manufacturers clearly state thet AGM batteries require ventilation.

There are a lot of AGM batteries out there living very short lives, because of failure to control charge rate and being used outside their recommended temperature range ..... this could have been avoided using a similar spec sealed maintenence free wet cell battery battery rather than a starved electrolite battery (what we used to call them before marketing made up the AGM label)

Because the AGM battery is starved of electrolite they can not cool them selves as efficiently..... thus the charge rate and temperature range is often limited.

Yes there are high charge and discharge rated AGM batteries out there with good temperature tolerance ...... but they are far more expensive than those commonly sold.

Please consider other options ....... there are good options other than AGM and at considerably less cost.

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Follow Up By: Tim F3 - Saturday, Apr 08, 2017 at 20:01

Saturday, Apr 08, 2017 at 20:01
Bantam thankyou for your considered reply,as a matter of interest the best deal i could find was 140 amp deep cycle batteries for $309 , these were "giant brand " with a 5 year warrenty.

I was focussed on AGM batteries as this is what the van manufacturer and many others suggested.

I thought they would accept charge more quickly than flooded wet cells , this appeared an advantage in a van that telies on solar charging as there is only approx 5 to 6 hrs of good sun per day.

But your argument makes sense to me , i will check out flooded batteries as you suggest,thankyou.
FollowupID: 879956

Reply By: Tim F3 - Monday, Apr 03, 2017 at 12:17

Monday, Apr 03, 2017 at 12:17
Ok results of load test are ...
Battery 1 has 65 amp
Battery 2 has 55 amp

So they are pretty well down , will have to look for replacements , might change to 2 x 130 or 150 amp batteries .

Thankyou to all who replied.
AnswerID: 609882

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