Charging batteries

[ccscott49]

I have seen some big chargers for sale, 27.2 volt 100 amp, they call them switch mode, constant voltage, constant current, but it doesnt state three stage or whatever, can somebody tell me whether this type of charger is the same as three stage or suitable for two banks, through a splitter or will I need to connect a smart charger between it and the batteries, (if there is such a thing for a charger) I'm at a bit of a loss here, as the chargers are cheap/reduced and big enough for me, they are advertised at <www.vikingmarine.co.uk/chandlery/> have a look for me I've asked for further details from them.

 

[Chris_Robb]

Yes looked at the post. - I think Swith Mode is normally the alternative description gven to 3 or 4 stage chargers. I installed a sterling and chucked out my old ferro resonant Constavolt (25 yrs old) - 20 amp demand. This was a good investment.

The advert is not clear just what these do - Charge mode equalization mode float, etc. Do they have cooling, will they provide a demand lead supply, etc.

Why are the so cheap - I suppose a 100 amp at 24V charger at £150 is incredible value - how is it cooled - Your boat sounds like you could be taking quite a demand charge off when keeipng the beer cold!

 

[bedouin]

Looking at the site I would say that it does exactly what it says - i.e. constant voltage/current (but of course you can't have both). Significantly it is described as 13.8V/27.2V - multi-stage chargers usually charge at over 14V for part of the cycle. The charger described will be as effective at charging the battery as a conventional alternator, but won't provide the additional charge rate/capacity you can get from a smart regulator.

Unfortunately there is no way I can think of to convert such a charger into a multi-stage device without taking a soldering iron to it.

As to charging multiple banks - yes you could, but avoid using a diode-based splitter. The voltage drop across the diodes would be so great as to render the charger almost useless. Either use a simple relay mechanism for parallelling up the banks while the charger is connected or go for one of these low-dropout splitters like the X-Split (and if anyone can tell me how they work, I'd love to know).

 

[ccscott49]

Tis true! My lecky requirements are high, but I do have the genny, I want to reduce the amount of runni9ng time on the genny, because I only have a jenelec 25amp charger, which just ins't man enough! I need 75-100amp unit, but a three stage jobbie, so as tom maximise the running time and keep my batteries in good nick. It's just at 150 squids, they are very good value, maybe I will have to go for the two outlet sterling jobbie, do they have a website?

 

[Chris_Robb]

How do you provide sufficient loading fro the generator if only battery charging. I understtod that Gensets need to be run at 60% min of Loading. Until mine packed up, I used to turn on teh immersion heater and a 1 KW Heater - just to load it up to prevent bore glaze.

 

[ccscott49]

I switch on the freezer, to super cool, which draws a fair amount, then of course tea making takes another 2kw! I drink a lot of tea, never been known to refuse a cup! Then theres the 12volt charger running aswell, so theres enough load on my 4KVA genny on and off, no signs of bore glazing, YET! But with a 100amp charger!Wow!

 

[ccscott49]

Just got the bumf from viking marine, they aren't three stagers, but still useful to some of us. Quote.

"These chargers were originally designed for the telecomms market and used to
power cell sites, 24hrs etc. They are therefore only float type, two stage
i.e. constant current/constant voltage. the current limit level is 100A the
voltage limit is 27.4V. This allows continuous operation without gassing the
battery and can be left permanently connected. However, the limited voltage
does increase the charge time. 80% capacity can be put back fairly quickly
but the last 20% takes some time.
There is only one controlled output which will charge paralleled batteries
but to charge at different rates will need a manual switch, a second charger
or a 'smart' splitter.
They are 5" x 8" x 13" with (internal) fan cooling along the 13" axis.
Weight is 9.5Kg.
Fully rated to 55C with internal temperature protection."

 

[ean_p]

not for your ordinary lead acid batts that need a controled and varied voltage/current...these are more suited to the esoteric batts like agm that need constant voltage within very clearly defind limits....

 

[ccscott49]

Thats what I thought, so it's back to an expensive one, do sterling have a website, I'm going to need a three stage 100amp model, at least 75 amps anyway!

 

[dickh]

Have you looked at the Adverc site? they also do chargers - www.adverc.com - very helpful.

dickh
I'd rather be sailing...

 

[gtmoore]

<A target="_blank" HREF=http://www.sterling-power.com>http://www.sterling-power.com</A> but it's not very good - have a look in the Download section as there is some info there


HTH

 

[hutch]

REYA Marine (www.reya.com) based in Cannes have a good range of switch mode chargers marketed under the brand "Dolphin" - up to 24V 160A, three stage, three outputs. Also have a 24V/50 amp charger with an additional 2 12V outputs.

Don't know anyone that has one and would appreciate feed back - in case I need to replace my own charger which is playing up. Otherwise have heard lots of good things about MasterVolt chargers - a Dutch company
<P ID="edit"><FONT SIZE=-1>Edited by hutch on 06/09/2002 02:09 (server time).</FONT></P>

 

[HaraldS]

Maybe you shouldn’t give up on these chargers so quickly. The telco market usually has quite tough specs, so they are probably very good quality.

Switch mode normally means they have a very low internal loss, or good efficiency, and they are probably not very heavy since they are using high frequency transformers. In other words they first rectify the AC, buffer that high voltage DC with a big electrolytic capacitor, and then use a MOS-Fet switch to create AC of a several kHz. That avoids the heavy transformer. On the secondary side they rectify again and they regulate the voltage by signaling the primary side to turn on and off. That’s where the switch mode name comes from. - Most modern power supplies or chargers work that way. Nothing special.

But I would guess that the regulation is adjustable, possibly over a little adjustable resistor, maybe by replacing a zehner diode. Drawings would help, but should be possible to figure out with these.

I would guess that you could adjust the output voltage in a decent range, probably to over 30V.

The 27.4 that they are set to are really near a normal float charge voltage and you wouldn’t get near 80% with a standard semi-traction battery, before it will drastically reduce current. At that voltage the 100 Amps are good for huge battery banks. I’m talking about several 1000 Ah. For you it wouldn’t charge any better than the 25 A thing you have.

But assuming you could change the limit voltage, you would almost get what you need. You would get a two-stage charger, that will boost charge until the limit voltage is reached and then bulk charge with a continuously dropping current. The only problem is it will not cut out completely to a lower float voltage after some time. But if you only use it while you run the generator, there is little to worry about, it is only the permanent laying in the marina mode that would be dangerous.

So you could set it to say 28.5V, which would charge your batteries at full current until about 85% full and then the current would ramp down gradually, and the batteries would gas lightly in that phase. (Like the first two stages of a 3 stage charger). It will take at least another 4 hours to pump in the remaining 15%. Eventually you would have to cut it off manually, but for keeping them maintained on shore power you have your existing charger anyway.

Assuming that you could set the voltage even higher, say to 29.2, you could allow for splitter diodes to your two banks.

I have a Victron charger with 75A for the same reason, (charging fast from the genny), and for my 420Ah 24V battery bank I could do with even more Amps. When I run the main engine, I can charge with 135A (big AmpTech Alternator) and the batteries happily take that. So usually when under way I cycle the batteries between 40% and 85%. That way I can maintain a daily cycle and run the generator about 2.5 hrs a day, the genny then usually also runs the heating element and the AC water maker. On days when I need to use the engine, I can forget the genny, and if I need to motor long enough, I get the batteries fully charged, The theory says that they need a full charge at least every 8th to 10th time, this actually seems to happen automatically, as I either need to motor long enough in say 8 days, or get connected to shore power. I let then gas a bit and have a collecting hose that brings the gas outside, and I think they like this little stir-up. The water consumption is still no problem and in three seasons I have run the water level down from full to half way towards the top of the plates. Just filled then again and each cell took about 200ml.

 

[ccscott49]

Interesting stuff, thank you. I haven't written off these chargers yet, but I don't really want to have to worry about switching off and having two chargers etc. I have a crew chappie during the summer and he's not the sharpest chisel in the toolbox, so I need a simple plug in and forget system, which needs little or no maintenace, I aklso have sealed batteries, so can't afford for them to lose fluid, theres no way I can top them up. I'm talking to a couple of peeps right now and will let you know how I solve this problem. thanks again for your input, it's just what I needed!
Colin.