Charging Auxilliary Batteries

Submitted: Sunday, Feb 26, 2006 at 22:51
ThreadID: 31194 Views:2706 Replies:13 FollowUps:23
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Hey there
Just after some opinions on battery charging when camping on extended stays.
My Scenario..... Have a Nissan navarra ST-R 04 model with 60 amp alternater.I have a battery iscolater installed witch runs 8mm B&S cable to the rear of the vehicle into an 50amp anderson plug. This is meant to charge two deep cycle batteries wired in parrallel (total Bank 150Amp hours)that are mounted on a camper trailer. Same wiring and adapters used on trailer as on vehicle with all the circuit breakers and so on and so forth in between. I gather by reading many posts on this website, that if they could make a 3 way fridge that could cool like a compressor fridge (ie Waeco) they would set the world on fire in sales. Unfortunately this is not the case.
My struggle is deciding whether to go a chescold 3 way or a Waeco. We go away regulary over weekends for 2 nites, but during holiday periods for 2 -3 weeks. I really want a waeco but i am not sure how efficiently my car will charge my batterries.
So basically my question is, after all that, if a Waeco fridge + lighting ect is using approx. 45 amp hours a day, how long would i have to run my vehicle per day to charge the batterries back up? I am just not sure how exactly alternaters put charge back in, i would like to think that it will put 60 amps per hour, but have a feeling this is not the case.
Would greatly appreciate feedback
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Reply By: Derek from Affordable Batteries & Radiators - Monday, Feb 27, 2006 at 00:29

Monday, Feb 27, 2006 at 00:29
Hi Freezer

Read my article on this topic for a bit of info and feel free to contact me if you wish.


With out getting too technical and setting Mikey and Cols out of control looking to run me down, you will need the following...

A good compressor fridge, Engel, Waeco or Evacool. 3 way fridges have their uses but mounted in a trailer could be a problem. I may also think that with all the bumps the trailer will get to go Engel. The swing motor can handle more knocks.

As to power and charging you are on the right path with your figures. 45 amps per day sounds close and you should require about 2 to 3 hours drive time per day to keep the batteries up to scratch.

There are variables so keep an eye on things and adjust acordingly. Possibly look at a solar panel to keep the batteries up when you are not traveling if the batteries are in the trailer and you stay in one place for more than a day or two.

Regards Derek.
AnswerID: 157232

Follow Up By: Mainey (WA) - Monday, Feb 27, 2006 at 02:14

Monday, Feb 27, 2006 at 02:14
Lash out and buy a decent Solar panel with a reliable, easy to use solar regulator that will be charging a large AGM Deep Cycle Aux battery and you won't have any problems.
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Follow Up By: Dilligaf - Monday, Feb 27, 2006 at 06:40

Monday, Feb 27, 2006 at 06:40
Derek if you can put back 45 amps into an auxilliary battery in 2 to 3 hours you are a miracle child. I dont think you know much about batteries or auxilliary battery systems.

Engel will not take more knocks and as a matter of fact the swing motor bangs crashes and fails.
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Follow Up By: Shaker - Monday, Feb 27, 2006 at 09:01

Monday, Feb 27, 2006 at 09:01
Quote: "Engel will not take more knocks and as a matter of fact the swing motor bangs crashes and fails."

What facts do you base this spurious statement on???
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Follow Up By: Ron173 - Monday, Feb 27, 2006 at 16:09

Monday, Feb 27, 2006 at 16:09
I agree with Shaker above here,

not many posts bout Engels failing on here, except once they are 20yrs old or so, plenty about Waeco fridges stopping, turbo system malfunctions, dodgy switches etc. the list goes on.

Sure the Engel costs a bit more, but show me a bloke who has one and says it wasnt worth the extra dough? Quality costs a bit more in anything.

The Waecos are reasonable and have their place in our fourbie world, but if your gonna get serious and subject a fridge to lots of off road vibes bumps etc the Engel takes it best. FACT. (search on here for fridge problems and it soon becomes clear that $200 extra is well spent)

I do await to hear how the swing motor bangs crashes and fails though????????


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Reply By: Member - Jeff H (QLD) - Monday, Feb 27, 2006 at 03:07

Monday, Feb 27, 2006 at 03:07
Just typed an epistle , and my dog rejected it.

My dog reckons a good solar unit supplies endless 'roo tail chunks
(By the way, is it possible that you and Col are the monkies on Dereks back ?)

I admire his will to survive, and wish both him and his customers total satisfaction.
Jeff H.
AnswerID: 157239

Follow Up By: Mainey (WA) - Monday, Feb 27, 2006 at 12:29

Monday, Feb 27, 2006 at 12:29
after reading your post I understand your dogs choice, L0L
and I also wish both him and his customers total satisfaction.
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Reply By: drivesafe - Monday, Feb 27, 2006 at 08:54

Monday, Feb 27, 2006 at 08:54
Hi Freezer, you would be lucky to get any significant charge back into the batteries in under 8 to 10 hours.

The first problem is the size of the cable. Without knowing the type of batteries you are using, you need to run at least 10mm2 to successfully charge a standard type ( wet cell ) deep cycle battery and for two batteries you would need at least B&S 6 ( about 13mm2 ).

Next your alternator is a bit on the small side but in any case it is not just the amount of power your alt can put out but the amount of current at the highest possible voltage that will charge your batteries correctly and as quick as possible.

In your case, the size of the cable and the type and size of the batteries and the fact that you will still be supplying power to the fridge means that you are going to have one hell of a voltage drop by the time you get to the batteries in the camper trailer.

No matter what type of batteries you have, this voltage drop is going dramatically reduce the charging capability of your batteries and will mean you need to charge them for a much MUCH longer time and 10 hours is being very optimistic.

Also,depending on the type of batteries, there are going to be other consideration that have to be taken into account.

Your present set up is most likely going to seriously shorten the life span of your batteries, no matter what type they are and would strongly suggest you seek the advice of a professional installer.


AnswerID: 157245

Follow Up By: FREEZER - Monday, Feb 27, 2006 at 18:53

Monday, Feb 27, 2006 at 18:53
The cable size we used is B&S 8mm, should be better than B&S 6mm shouldnt it?
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Follow Up By: drivesafe - Monday, Feb 27, 2006 at 19:50

Monday, Feb 27, 2006 at 19:50
Hi Freezer, confusingly, the smaller the B&S number, the thicker the cable sizes.

B&S 8 = 7.9mm2 while B&S 6 is 13.5mm2, the exact size will vary slightly between manufactures.

Do a google search for B&S and don’t put spaces between the B&S. You can also search using AWG ( American Wire Standard ) as these two measuring codes are identical.

Wire sizing in Australia is a bit stuffed as there is no mandatory code set for automotive cable sizing like there is for AC domestic cable.

By the way, what type of batteries are you using.

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Follow Up By: drivesafe - Monday, Feb 27, 2006 at 20:05

Monday, Feb 27, 2006 at 20:05
Hi again Freezer, I have just looked at your post down below this and see you are running wet cell batteries, as posted, to get better charging results and to reduce the charging time you would be better set up if you fitted at least B&S 6 cable and invested in a larger alternator.

Works out a lot cheaper than going solar, now before all the solar enthusiast come a running, I personally prefer solar but for most the cost is just not warranted.

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Reply By: Boo - Monday, Feb 27, 2006 at 09:00

Monday, Feb 27, 2006 at 09:00
Morning Freezer..

I'm no expert, dont have a 4by shop or sell books, but I did have the same problem when deciding on our setup.
The path we decided to take was to use a 50lt Chescold initualy, we have a camper with 2 x 120amp deep cycle batteries as well as a dual battery system in the trol all wired through with 200amp cable and 175amp anderson plugs (dont believe in half doin things). We often get away for the short 2 or 3 day weekends and have the fridge running happily from the batteries but anything longer than that and we allways connect the fridge onto the gas and we dont have to worry about how the batteries will last then. Its a lot cheaper to go the 3 way than have to buy solar etc, and its hassle free apart from refilling the gas bottle before we go. We just recently bought a 70 lt Downunder as well and we generaly leave it sitting in the back of the vehicle and use it as a freezer when away for extended trips and use the 3 way on gas as a fridge setup at the kitchen unit, that way its using minimum power and not being opened constantly.

Hope that gives you some food for thought..
AnswerID: 157248

Follow Up By: FREEZER - Monday, Feb 27, 2006 at 19:09

Monday, Feb 27, 2006 at 19:09
Afternoon Boo
Thanks for your reply, i definately agree with the conveinience and hassle free, of a 3 way. No worrying about flatening batteries. I am just a bit wary as from the posts i have read on this site, a lot of people are saying that they can struggle a fair bit in hot weather. I live in Qld.
My main problem is i took father in laws advice in getting this battery icsolator set up, and given it is a fair setup, but really only good if your touring, and on the move every couple of days. This is not our case at the moment.( Cant really drag the camper trailer around every day to charge batteries once set up for two weeks on morton or fraser.) So i my only other real option if getting a compressor fridge is to get a 80watt solar panel. $800 later. Bit of a kick in the guts after spending money on alternator system.
I wonder if a Gen set and batery charger would work?

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Follow Up By: Member - Norm C (QLD) - Monday, Feb 27, 2006 at 19:37

Monday, Feb 27, 2006 at 19:37
Gen set and 3 stage charger will certainly work Freezer. The 3 stage charger is also great for a good charge when you have access to 240V.

Downside? Some National Parks and camp grounds don't permit gennies. Also, even when permitted, you need to consider campground etiquette if near others.

If I understand your set up, you don't have a DC in the vehicle. If you add one, it will charge every time you drive. Make up an extension cord to run to the fridge. This will give you another power alternative if the CT batteries are run down, but you have been for a good drive during the day.

This is how I am set up. I have two DCs (AGMs) in the CT and one DC in the vehicle. I have set up so I can run anything from any battery. I am currently making provision so I can move one of the CT batteries to the vehicle if I want for a particular trip and have two in the vehicle and one in the CT. Flexibility is important in my view.

I actually prefer the fridge in the vehicle. Cold beer and lunch available no matter where you are. And if you drive to town for some shopping, you have the fridge available for the cold stuff. Also your main power drawer (fridge) is near the most efficient charger (alternator) which gives free charging every time you run the vehicle.

But we all have different views and sometimes circumstances dictate a set up. You can only play the cards you are dealt.
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Follow Up By: Boo - Monday, Feb 27, 2006 at 21:18

Monday, Feb 27, 2006 at 21:18
From our experiance witrh the Chescold 50lt, you wouldnt have too many problems with the temp not getting down enough. We were using ours over xmas when the temp was around 38 - 40 and we had to turn it down as far as we could so the contents wouldnt freeze. We find on gas (or 240v) its extremely effective cooling even in the hottest conditions. On 12v it will maintain temp but doesnt drop the temp overly well.
Personaly from our experiance I cant fault the Chescold unit even in very hot conditions.

The way we use our sytem..
We leave the 12v Downunder in the vehicle running off the dual battery sustem which recharges when and if we go for a drive, if we dont do any driving I leave the car connected to the larger batteries in the camper which runs the fridge/freezer (Downunder) and camp lights. The Downunder in the back of the car running on 12v is used as a freezer that way we arent opening it more than once or twice a day to move stuff into the other fridge unit running on gas we set up beside the kitchen at the camper.(which is the 3 way Chescold unit). After about 8 - 9 days we have the option then of moving anything thats left in the freezer into the Chescold to minimise the remaining battery life just for lighting which could if needeed run the lights for another 4 or 5 days without charging and still have things cold and frozen in the Chescold.

Hope that helps..
If you need any info on what lights etc. I'll give you my email address and give you a more detailed run down and some picies..
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Reply By: Member - Paul P (Bris) - Monday, Feb 27, 2006 at 09:06

Monday, Feb 27, 2006 at 09:06

My expereince tells me your alternator is too small in capacity for what you are trying to achieve. I replaced a 65amp/hour on a four runner with a 120amp/hour because of this problem(lack of charge capcity). Alternators are fairly cheap. See you friendly vehicle sparky or mechanic.

Compressor type fridge would be my choice. I have a personal preference for Engel.

You will still have problems with extended stays without 240volt power without running your vehicle for at least 2/3 hours ( with a bigger alternator ) daily/every second day. Solar would be the way to go to address the extended stay issue unless you wish a generator (not a fan of those in camping areas).

You will still need a bigger alternator as the charge requirements really exceed the capacity of the OEM one.

My thoughts


AnswerID: 157251

Reply By: Mike DiD - Monday, Feb 27, 2006 at 09:32

Monday, Feb 27, 2006 at 09:32
Brett - are these DeepCycle batteries conventional wetcell with filler caps or sealed AGM batteries.

How fast you can charge them from Alternator or generator will depend on the battery type.

If you are thinking of Solar keep in mind that it will be EXPENSIVE - an 80 watt panel puts out 4.5 amp MAXIMUM.

Be clear that instantaneous current flow is AMPS (like Litres per hour) and that total current flow is AMPHOURS (like litres). That is why battery capacity is in AMPHOURS.

AnswerID: 157256

Follow Up By: FREEZER - Monday, Feb 27, 2006 at 19:17

Monday, Feb 27, 2006 at 19:17
They are filler cap ones. Yeah i know the solarpanels are exy, thats why we didnt go down that track originally(although i really like the concept).
I went the alternator way on someone else knowledge and didnt look into the efficiency and practicality of it in our camping situation until after i got it. Dumb i know! But usually the father in law does know everything, maybe its been a big facsade all these years LOL
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Follow Up By: Mike DiD - Monday, Feb 27, 2006 at 19:56

Monday, Feb 27, 2006 at 19:56
Brett - since they are wet cell DeepCycle, they will limit how fast you can charge them.

It would take at least 5 hours to charge them fully, but you are only taking out about 50% of the capacity. There's no point in upgrading your Alternator - the batteries won't be able to take more current.

Especially with such a long run of 8Ga - you should really upgrade to 4 Ga to keep the voltage drop down so there is enough volatge at the batteries to charge them.

Make sure you check the Alternator voltage at the front batteries when at fast idle - if it's less than 14.4 volts you will have very slow charging.

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Follow Up By: drivesafe - Monday, Feb 27, 2006 at 20:59

Monday, Feb 27, 2006 at 20:59
Hi Mike, while I agree with you on the cable up grade, Freezer would definitely benefit from an alternator up grade as well.

There are a number of problems that come with having a small capacity alternator and the first is that the vehicles engine revs are going to need to be around 2,000 rpm for him to get any where near 60 amps and as most alternators are rated at their maximum output not the continuos output then Freezers alternator is probably flat out producing 50 amps.

Because of the likely hood that the engine is not going to be at maximum rpms for the alternator to be able to put out 50 amps, the lower amps will be required to power quite a few things, particularly at night so Freezer will be very lucky to be getting 14 volts while trying to charge his batteries and running everything else, including his fridge.

A 100 amp alternator would be far better as it would be able to put out the amps needed at a lower engine rpm and more importantly, much higher volts.
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Reply By: Derek from Affordable Batteries & Radiators - Monday, Feb 27, 2006 at 09:41

Monday, Feb 27, 2006 at 09:41
Monkeys, snakes in the grass all the same to me.

I work from experience, field testing and satisfied customers.

I don't presume anything. I test and build to suit. I have customers that rely on my systems and wiring and go places most of you only see in magazines.

I own a Waeco but must admit the Engel is a better fridge. My own CF80 has stopped when hitting a big bump in the road.

I do think I can work miracles for my customers and on this very forum you will read feedback from happy customers.

Field testing is a big part of my product design and suggested rating on batteries and charging systems.

Tables, graphs, web searches don't mean much in the bush. You know it all couch potatoes should try it some time.

This forum is about advice and help.

Regards Derek.
AnswerID: 157258

Follow Up By: Ron173 - Monday, Feb 27, 2006 at 16:13

Monday, Feb 27, 2006 at 16:13
G'Day Derek,

Well theres a thing, a man who owns a Waeco but admits Engel are better!

Question for you, can you put an AGM in as your aux battery when your main is still a wet? (wired through an isolator/charger of course)


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Reply By: tdv - Monday, Feb 27, 2006 at 10:28

Monday, Feb 27, 2006 at 10:28
I'm no expert and had a preference for compressor fridges as I've used them for work (Waeco) without any problems. However I recently purchased a camper trailer that came with a Chescold fridge/freezer in a fridge box on the front. I was skeptical but thought I should try it out before deciding.

Despite all the stories that they don't get cold, leveling is a pain etc I have found (2 long weekend trips) that it has been fantastic. Even too cold at times (and I live in North Queensland). 1 x 9kg gas bottle is supposed to last 2-3 weeks and I run from the car while driving via anderson plug. I have been careful not to load up with hot beers all day though as I've been told they have trouble pulling down lots of hot stuff in one go.

So I've decided to keep it.....and maybe in the future buy a small 25-30l compressor fridge to run for the days I'm very thirsty!


AnswerID: 157268

Reply By: Member - Norm C (QLD) - Monday, Feb 27, 2006 at 10:49

Monday, Feb 27, 2006 at 10:49
Freezer, I won't comment on fridge choice. But I can confirm the view above on cable size when charging batteries on the CT.
If you do a search there is heaps of info on this on this site. Some of it on threads from the last week or two.

I have a 105AH standard wet cell DC in engine bay and two 120AH AGM DCs on the CT. Connected via double insulated welding cable (about 25mm squared) and 175 Amp Anderson Plugs.

Works well and worth the initial effort. I believe most problems with charging DC batteries and running fridges stem from poor installation and insufficient cable size.
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Follow Up By: FREEZER - Monday, Feb 27, 2006 at 20:14

Monday, Feb 27, 2006 at 20:14
i am not an expert by any means when it comes to auto electrics, so this question may sound as dumb as dog S@#t, but is 8 B&S cable better than 6 B&S cable. I thought the higher the number the thicker the cable
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Follow Up By: drivesafe - Monday, Feb 27, 2006 at 20:38

Monday, Feb 27, 2006 at 20:38
Hi again Freezer, most cable in Australia does have the square area marked on it, not all though.

If you have an idea of the maximum current requirement of a given circuit.

If you know the maximum current you need, to reduce voltage drop and give the circuit a decent bit of safety, multiply the maximum current by 3 and then try to match the current required to a suitable cable size.

You can do a google search and get some handy cable comparison charts to help you workout what you need.

With cable that is going to be used for charging batteries, it is better to go to even larger sizes and in this case bigger is MUCH better.

Your 8 B&S is the minimum size that would be used to charge a battery in the vehicle but is to small to adequately charge a single battery in your trailer.

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Reply By: Steve & Mish - Monday, Feb 27, 2006 at 19:34

Monday, Feb 27, 2006 at 19:34
We have bounced an Engel fridge for years - great machines, stand up to punishment and the newer ones are very efficient.
We have studied the power dilemma and have come up with the idea that we run the fridge from the car battery and start the engine every day and run it for 40 mins or so. Has worked fine so far (short trips). We also carry jump leads and until recently, one of those rechargeable jump starters - but that was useless (from supercheap). I believe the advantage of this set up is that the single, main battery will get charged up much more quickly than a second one in a dual bat set up. Disadvantage is that the battery doesn't like it and will have a shorter life (and it's probably not so good for really remote areas!).

I rekon we may have had the ultimate set-up on our old Landy - two alternators running two completely separate charging systems.
AnswerID: 157348

Reply By: Gu_Patrol - Monday, Feb 27, 2006 at 20:24

Monday, Feb 27, 2006 at 20:24
I still think the solar panels are far too expensive compaired to a 1kw genarator, a solar panel will only give you so much power, at least you can start the gen at anytime and you also can run other things of it.

When the solar panels are half the price of what they are now they might be worth buying, they haven't come down in price since they where first invented, It's all crap when they say it's expensive to manufacture solar panels, the bloke who invented it get most of the money .

Otherwise get a good second alternator in your car
AnswerID: 157359

Reply By: FREEZER - Monday, Feb 27, 2006 at 20:44

Monday, Feb 27, 2006 at 20:44
I keep finding out infomation that makes my alternater charging setup basically a waste of money and time. Wrong setup for situation, wrong cable for wrong setup, small alternater, even small anderson plugs. Never again will i asume that someone else knows what the best setup is for me. I think i might have to resign to a 3 way fridge and use batteries for lighting and other little knick knacks. Maybe alternater may be able to keep up with the little i take out of batteries with lights etc. Thanks for everyone insight although i do wish i could come to a more optomistic conclusion. Oh well, it all a learning experience

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Follow Up By: drivesafe - Monday, Feb 27, 2006 at 21:11

Monday, Feb 27, 2006 at 21:11
Couple of points that may lighten the load.

If you have a good quality battery charger at home, if you charge the batteries up before you go for you shorter trips, your alternator will have no problem keeping them fully charged while you are getting to where you are going.

Next, again if you have a battery charger, take it with you and you may be able to extend the operating time of your batteries while you are away.

As for the Anderson Plugs, if they are SB50s then they have a continuos rating of 50 amps which is heaps big enough for your set up. There is no way you are ever likely to pull more than 50 amps even with two flat batteries and the fridge running.

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Follow Up By: MikeEgan - Monday, Feb 27, 2006 at 21:52

Monday, Feb 27, 2006 at 21:52
I have a Chescold freezer we use as a fridge and works in all temps in NQ. Bought a 55w solar panel for $500 a regulator for $120 and 60 amp gel battery. Powers my fluoro lights and small LCD TV. Have had the solar panel for a year and returned last week from 7 month trip and battery never went flat once. The battery is only charged on the small caravan by the solar panel.
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Follow Up By: drivesafe - Tuesday, Feb 28, 2006 at 06:03

Tuesday, Feb 28, 2006 at 06:03
One more point and slightly of subject, I don’t know how long you leave your trailer between uses but if it’s anything more than a 3 or 4 weeks at a time, your batteries would benefit from having a maintenance charge on them during these non use periods.

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Follow Up By: FREEZER - Tuesday, Feb 28, 2006 at 09:51

Tuesday, Feb 28, 2006 at 09:51
yeah i have them connected to a 10 amp charger, it does a boost charge to 80% capacity then Float charges until full, then maintains batterry as needed

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Reply By: Sand Man (SA) - Tuesday, Feb 28, 2006 at 02:06

Tuesday, Feb 28, 2006 at 02:06

Nobody has suggested you consider the Arrid Twin Charge unit, so I will.

This unit is basically a DC-DC Converter that will overcome the voltage drop problem. It will accept a lower input voltage and output a higher voltage necessary to obtain a full charge back in to the auxiliary battery(s).

This device is a common and practical method of coupling remotely located batteries in campers and caravans to the vehicle's charging system.

I'm diagonally parked in a parallel Universe!

My Profile  My Blog  My Position  Send Message

AnswerID: 157439

Follow Up By: drivesafe - Tuesday, Feb 28, 2006 at 05:58

Tuesday, Feb 28, 2006 at 05:58
Hi Sand Man, in Freezer’s situation devices like that would actually take longer to recharge the batteries and remember, on top of charging two batteries, he still has a fridge to run.

For about the same expense, as suggested above, he would be far better off upgrading his cable and alternator.

They are only effectively time savers on small batteries up to about 70 amps and once you get over 100 amps they will NOT speed the charge up and they will take longer than a properly set up dual battery system will when running straight off the alternator.
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Follow Up By: FREEZER - Tuesday, Feb 28, 2006 at 10:05

Tuesday, Feb 28, 2006 at 10:05

I have become a little uninspired when it comes to my alternater setup, even if i do as you suggested with the upgrades in alternator and cable. I still question its effectiveness in keeping my battery bank topped for 2-4 week stays. If i was only staying in one place for a couple of days then moving on it would work well, but with a couple of littlies they would not enjoy it asmuch as i would. I am now thinking:
1. Get 3 way fridge, and run only lights,lcd screen, pump taking around 10-12amps per day. The alternater may handle this in a better time frame.Could even get a 20 watt solar panel to help or:

2.Get compressor fridge and charge battery bank (2 x 75Amphour wired parralel) from gen set. (not sure how long this would take if using 40-45 amp per day)
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