A question of Battery power ..

This has me stumped so I hope someone can advise ..

I have a battery box containing 3 X 7 aH UPS batteries which I use in my camper for internal lighting ..

I also have a 26 aH UPS battery which I use at home for testing polarity etc etc ..

I tried to run my Waeco CF50 on the 26 aH and it kept going into red flashing error mode BUT the 3 X 7 aH powered it no problem at all ..

All of these batteries hold charge and appear to be OK but I can't figure out why the bigger one fails at running the fridge ... It has a 7.8 Amp rating stamped on the side so that should be OK for a 4 Amp fridge ...

And before you all jump to the wrong conclusion - I run the fridge from a 100 aH in the back of the Jeep under normal use..

This was just a test I was doing ....

Any ideas ? I assume the 26 aH is unwell ?

Cheers

Steve
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Reply By: Notso - Monday, Jan 25, 2010 at 19:28

Monday, Jan 25, 2010 at 19:28
Just check the battery voltage when you are trying to run the fridge, if the battery voltage at the battery terminals is up around the 12.5 + area then there is something wrong with the connection. If the battery voltage at the battery terminals reads down around the 11 or so volts then the battery has had it.



AnswerID: 400992

Follow Up By: Mandrake's Solar Power- Monday, Jan 25, 2010 at 20:05

Monday, Jan 25, 2010 at 20:05
Notso ,

You're a genius - I've been lookin an lookin an not seein the obvious !!

The connections was through ciggy lighter sockets - which I assumed were the same !! I just bypassed the socket and fridge runs !!
Connections on that ciggy plug dropped the voltage to 11 !!

Cheers mate - I owe you one !

Mandrake
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FollowupID: 670261

Follow Up By: Notso - Monday, Jan 25, 2010 at 21:07

Monday, Jan 25, 2010 at 21:07
Aint it nice when it all comes together EH!
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FollowupID: 670276

Reply By: Member - Allan B (QLD) - Monday, Jan 25, 2010 at 20:22

Monday, Jan 25, 2010 at 20:22
Those cigar-lighter sockets are bad news. The main problem is that the positive centre contact does not have a wiping action to clean the contacts. It simply pushes the spring-loaded pin against the contact in the socket. Any oxide or dirt on the contact faces is simply compressed but remains to interfere with a good contact connection. Best to get rid of them.

Merit type sockets on the other hand, although similar in appearance, do have a wiping action of both the positive and negative contacts. They are more reliable but do have limited current-carrying capacity.

Cheers
Allan

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AnswerID: 401002

Reply By: SNAKE No1 - Monday, Jan 25, 2010 at 21:25

Monday, Jan 25, 2010 at 21:25
Hi Steve,
Do yourself a favour mate and use Anderson plugs.No more worries.Check out Derek who has an ad on this site. Cheers Snake
AnswerID: 401017

Follow Up By: Mandrake's Solar Power- Monday, Jan 25, 2010 at 21:34

Monday, Jan 25, 2010 at 21:34
Cheers Snake -

I sell them too !

Rgds

mandrake
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Reply By: olcoolone - Tuesday, Jan 26, 2010 at 14:42

Tuesday, Jan 26, 2010 at 14:42
I would say you may have one cell failing.

Try doing a load to maximum discharge test and see how many amps you can pull out of the battery.

Try it with a 2 amp load and then a 10 amp load and calculate the average or work it out from the SOC and discharge load spec from the battery supplier.

Or use a electronic battery tester.
AnswerID: 401115

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