Bow thruster batteries - urgent advice needed

Observer

Observer

Well-Known Member
Joined
21 Nov 2002
Messages
2,781
Location
Bucks
Visit site
Bow thruster died assumed because of low battery charge. It's been on charger for several hours but thruster is barely whirring.

The DC system is 24V so two batteries needed. Have changed one of the bow thruster batteries for one of the stern thruster batteries. Bow thruster now OK but no life in stern thruster so conclude the battery I swapped over is dead. I propose to buy one replacement battery to replace what appears to be the dead one. Questions:

1. As bow thruster is now working, can I assume the second battery is also OK?

2. If second battery not OK, will it drag down the new battery?

3. The exisitng batteries are 120Ah. Is it OK to replace with a 110Ah?

Also intend to put a multimeter on all of them to check the charge state.

Anything else I should do/not do?
 
no
yes
yes

fully charge (ie timewise) leave for a hour to stabilise then check the SG. voltage w ith a muiltimeter will give an indication (take it 1 hours after ceasing charge then again 2 hours later for example - any further drop and it's probably not going to hold charge!) , better still put a load like a car headlight bulb across it whilst measuring voltage - if it powers up th ebulb but does drop drastically it looks good............
 
Tuther way is, take the tops off, then put a sleel bar across the terminals and see if one cell smokes.

I've seen batteries tested all sorts of ways. But there still duff. Sometimes 14 volts but no amps.

Personally for a bow thruster, I'd get two AA bateries and chuck them in the sea. /forums/images/graemlins/laugh.gif
 
if your battery is rated in amp/hrs, it sounds like you have a type of leisure battery. If so, then you have the wrong battery type for this job and all you r batteries will fail sooner rather than later. Leisure/domestic batteries are designed to provide a little power over a long time, and thus are rated in amp/hr capacity. The type of battery you need is one where the plates are strong enough to take the very high amp flow required. Thus the correct battery type is normally rated in CCAs (Cold crancking amps) a normal engine start battery is constructed like this, or you can go the carbon fibre reinforced plate route for optimum capability. i.e. batteries such as Trojan or elecsol, but these will be somewhat more expensive. You should have the battery spec in your bowthruster literature, and it should be something like 800 CCA
 
DO NOT DO THIS!!!
"Tuther way is, take the tops off, then put a sleel bar across the terminals and see if one cell smokes."
There is a very good chance the battery will explode and cover you and everything around you in ACID!

Take it to a car shop and they will test it for you free of charge.
 
Told you it would be knackered... /forums/images/graemlins/laugh.gif /forums/images/graemlins/laugh.gif

What do you mean. Used to do it all the time!!! /forums/images/graemlins/crazy.gif /forums/images/graemlins/crazy.gif
 
Check out the requirements of your thruster, i have a vetus 55 the min power is 110ah, was a retro fit and marina put in a 95ah had to upgrade as the 95ah would not give enough bite, put in 115ah & happy days super job.
 
[ QUOTE ]
i have a vetus 55 the min power is 110ah, was a retro fit and marina put in a 95ah had to upgrade as the 95ah would not give enough bite, put in 115ah & happy days super job

[/ QUOTE ] I struggle to understand how the storage capacity of the battery (Ah) can impact the performance of an electrical motor designed to be run in very short bursts and when connected to an active charging source too (ie engine running / alternator)

/forums/images/graemlins/confused.gif
 
Because 110Ah and bigger batteries tend to be a physically larger package also capable of delivering higher current (rated in various ways, CCA = cold cranking amps).

Many of the 95Ah/100Ah batteries have almost the same capacity, but substantially lower max current capabilities.

dv.
 
couldn't agree more it's a CCA or Amp thing but it's not per se an Ah thing - but would add that many 85Ah units are built to deliver many more CCA than your average 110 unit does - and they are not always physically bigger.
 
DO NOT DO THIS!
THE PLACE A STEEL BAR ACCROSS THEM!!
THERE IS NO QUESTION ABOUT IT.
THE BATTERY WILL EXLODE, I HAVE SEEN IT HAPPEN, WITH A SO CALLED EXPERT ENGINEER HE SURVIVED LUCKILY.
THE BATTERY WAS ALL OVER THE ENGINEROOM
 
as others say , the multimeter won't tell if battery knackred: they can still show 12 or whatvr volts on a multimeter. Likewise (tho er bit different) teensy battery and giant battery can show same volts.
 
The battery experts do something very similar to this. They have a gadget, called an instant discharger or something similar. You put one of the spikes on each battery terminal and it causes a dead short and gives you some sort of reading on the meter that sits on the bridge between the two handles. The clever bit is that there's some gizmo built-in that stops the battery/the device/the operator being blown apart. With apologies for the lack of precision in this explanation!
 
For a 24v system, I'd recommend to change both batteries if one is duff or if the batteries are more than 3 years old. Getting 2 the same means that the charging rate for both will be the same and this will prevent one battery getting overcharged while the other is undercharged.

As for what type of battery, I think starting batteries with thin plates (high CCA) would be required as bow thrusters can draw 500amps.
 
The reason they don't blow themselves up is that is doesn't produce a dead short, but a controlled load, normally 75A, not the several hundred that you could get with your spanner or steel bar.

Please don't actually try the spanner or steel bar thing. Best case is crispy fingers as the bar warms up a lot. Worst case is bits of battery casing being chucked around at high speed followed by a face full of concentrated Suphuric acid, which doesn't do much for the complexion.

####

discharge.jpg


12V / 24V BATTERY DISCHARGER

Lester Electrical is pleased to announce the addition of Model #25270, a 12V/24V Battery Discharger to its current product line. Prior to this addition, the Lester Electrical product line consisted of Model #17770, a 36V/48V Discharger, and Model #18400, a 36V Discharger.

With the addition of Model #25270, a more complete range of battery voltages is served. Like our other Dischargers, this model runs without AC input so there is no need to drag around extension cords or find an outlet to plug into. This discharger is also electronically controlled with a built-in microprocessor that automatically determines the battery voltage being tested. It can be programmed to shut off based on voltage or time and the discharge data can be viewed on the LCD display or downloaded to a computer with the built-in RS-232 port.

Large 500-amp alligator clips, heavy-duty DC cables, and an 18G powder-coated steel case ensure years of trouble free use. Made in the USA, this product is simple to operate and the testing cycle is automatic, shutting off automatically when complete.This Discharger discharges at 75 amps, following accepted industry standards.

####
 
You must log in or register to reply here.

Share this page

Top